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Ch 7. Laws of Variation: Varieties & species compared.

We have seen in our first & fourth chapters that changed conditions of existence, especially if accompanied with excess of food, seems to be a main cause of variation. But it must be owned that we are profoundly ignorant in regard to the origin first cause of variation. We do not know, whether the change in the conditions must be in some degree abrupt to cause much variation as I think may, perhaps, be inferred from such changes alone affecting the fertility of organisms; or whether a much slighter change prolonged over a longer period would not be equally effected effective. We can assign no sort of reason why one organism varies greatly under domestication, & why another varies hardly at all: why in a state of Nature, most, but not all the species of particular certain whole groups are excessively variable; & we do not even know whether this latter sort of protean variation is the same as ordinary variation. Ignorant as we thus are in regard to the primary cause of variation, yet when varieties do appear, we

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(Ch 7. Laws of variation)

can sometimes, in a very dim & doubtful manner point out some of the laws governing the changes in structure variation, as was attempted in the first chapter. Here I shall further treat on this subject; & compare domestic varieties with those naturally produced, & both together with the forms called by naturalists species.

If it can be shown, even partially, that species differ from each other in a similar manner & apparently according to similar laws, as do varieties, it obviously strengthens our view, that species are only strongly marked varieties with the intermediate gradations lost. The old cosmogonists believed that fossil shells, resembling but not identical with living shells, had been created within the solid rock; & they asked why God should not have thus formed them? The palæontologist now would probably now reply, that we see in the fossil & living shell plain evidence of similar structure, & therefore he would affirm that their origin & formation must have

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(Ch 7. Laws of variation)

been alike. So I believe that the similarity of the laws in the formation of varieties, & in the so-called creation of species, indicates that varieties & species have had a like origin; & not that the one has been due to the nature of surrounding causes, & the other to the direct interposition of the Hand of God.—

The laws which obscurely seem to govern variation, & which were briefly alluded to in our first Chapter, together with some others not then mentioned, may be grouped under the following heads. (1) The immediate action of the external conditions of life. (2) The effects of habit & disuse (3) The correlation of growth, namely the manner in which the modification of one part affects another part, either through quite unknown relations, or by such relations as that pointed out called by Geoffroy St. Hilaire & gather balancement or compensation, by which the large development of one part is supposed to cause the reduction of another; or by such as the early arrest of development in a part,

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Lastly, varieties occurring most frequently amongst this species those species, which are most closely allied that is those which fall into the larger genera—also amongst the more common species, (or those which are the most vigorous in any region & are consequently most abundant in individual members?) also amongst those which have widest ranges. Generally it

It, also, seems that the same species in the larger genera, are apt not only to be the most variable but to have the widest ranges & to be the most abundant in individuals. From the facts to be given under the last head

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[text excised] we gain, if the view that varieties & species do not essentially differ be true, a slight but deeply interesting prophetic glance into the far future of the organic world; we can dimly see whither the laws forms of life are tending; where about in the great scale of nature where new species will arrive, & where old forms will tend to disappear.

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(Ch 7. Laws of variation)

which, however, seem of more importance, however in monstrosities than in varieties;— the period, at which any modification supervenes, any early change of structure affecting parts subsequently developed;—multiple parts varying strongly tending to vary in number;—homologous parts varying in a like manner & tending to cohere &c.— (4) Parts developed in any species in an extraordinary manner & rudimentary parts tending to vary. (5) Distinct species presenting analogous variations; & the a variety of one species, resembling in character a de another species: reversions to ancestral forms. (6) specific The distinctive characters more of varieties more variable than specific characters; specific characters more variable than generic: secondary sexual characters may variable. (7)

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(Ch 7 Immediate action of external causes)

The immediate or direct action of external conditions.

When we find that certain individuals of a species placed under peculiar conditions, are all or nearly all affected in some particular manner, especially if all are soon affected, & more especially if the modification does not seem of any use to such individuals, so as to be that probably it is not the result of selection, then I should be inclined to attribute the modification effects to the direct action effect action of the conditions of existence. But it is most difficult to eliminate the power of selection:

selection.)

(From the facts given in the first chapter, I think we may in some case attribute greater size, early maturity, & the nature of the hairy covering &c to the immediate action of food & climate.

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thus we have reason to believe that climate produces some ef immediate & direct effect on the woolly covering of animals; & of but when advantage of this were is taken by man & a very long-wooled animal is produced by artificial selection, it would be wrong to attribute such wool to the immediate action of climate; & so it would be in the case of natural

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(Ch 7 Immediate action of external causes)

The time of flowering in plants, & & th those of breeding in animals no doubt is affected by climate; & a more curious difference has been observed in a in the same species of Lizard, being namely that it is oviparous in dry northern Chile & viviparous in humid southern Chile.*(*M. Gay, Annal. des Science Nat. Zoolog 2d series. Tom V. p. 224.) But in such cases we can seldom, perhaps never, separate the various elements in the conditions causing of change; we cannot tell whether it be cold or damp or lessened or different food which has produced any given result. The wretchedly dwarfed & often distorted state of state of the the shells in the Baltic may be safely attributed to the brackish waters; for the shells grow more perfect as they approach the open sea. N Few naturalists, however, would rank such shells, or the stunted plants on a lofty mountains, as varieties: But I can hardly see where to draw a line of separation: I presume that it is assumed that these dwarfed states are not inhabitable hereditary; & this would be a valid distinction; but we have previously seen how difficult it is even to conjecture what is hereditary inherited in a state of nature.)

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(Ch 7 Immediate action of external causes)

(In some cases of shells having an immense range, as that of the common Buccinum undatum from the North Cape to Senegal, *which presents a perfect series of intermediate var grades between the extreme northern & southern forms; I presume that the modification may be [illeg] attributed to temperature: but in cases, where we have a strongly marked variety, at the northern & southern ends of the range, with a narrow zone having inhabited by an intermediate state form, of which I have observed marked examples with cirripedes, it would be rash to attribute the difference to climate, for natural selection probably has come into play & according to my views is in the act of making two species. In regard to colour, Forbes (Report Brit. Assoc. on British Marine Zoology 1850 p. 254) says "it is easy for the practised conchologist to distinguish specimens of the most painted shells, gathered on the southern coasts of England, from those taken on other parts of our shores:" So it is in a marked degree certain with the tints of certain species shells, specified by him, which range from the shallow laminarian zone into great depths.

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 *Annales des Sciences. Nat. 2d series Zoolog. Tom V. p. 291.

[For readability the paragraph which Darwin scored is left undeleted]

(a) some most naturalists would not call these shells a variety nor would they a stunted plant going up a mountain, but I hardly can see where to draw the line of separation, I presume it is assumed that these forms are not in the least inherited, & if this be so it wd make a valid difference, but we have previously shown how difficult it is to conjecture what is & in a state of nature

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It is well known that in fur animals with fur, the skins are much more valuable, the further North they are collected.*( *Bell's British Quadrupeds on the Ermine Stoat: see Bronn's Gesichte der Natur. B. 2. s. 87.) In plants several cases are on record of the same individual or all its seedlings changing in a few generations, without the aid of selection, the tint of its flowers when brought from its native home into our gardens. *(c) (D) text) Moquin Tandon gives some instances of plants acquiring by variation more fleshy leaves, when growing near the sea. *d (*d Elements de Teratologie végétale p. 73). It has often been asserted that the same plant is more woolly when growing on mountains than on lowlands, & Moquin Tandon*(*f Ib. p. 62) asserts that this change occurred with several species from Pyrenees when placed in the Botanic Garden at Toulouse: but Dr Hooker informs me that the Anthyllis vulneraria is glabrous in the Alps & woolly on hot dry banks.

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(In the case of insects, if we read read the accounts given by Oswald Heer*(a) & Wollaston on the changes which insects the same species undergo in ascending mountains, & in approaching the pole, generally but by no means always becoming darker-coloured we can hardly avoid attributing the change to climate. So again, Mr. Wollaston*(b) clearly shows that residence near the sea-coast tends to make insects lurid, & affects them in other various ways. In regard to Birds, it would be easy to give several cases; but I will suffice to quote Mr. Gould, (Zoolog. Soc. Meeting May 8. 1855) whom no one will accuse of running varieties together, & he says that birds of the same species are brighter coloured in the interior of continents than near the coast, which he attributes to the greater clearness of the atmosphere far from the sea.*(z)

[Faint pencil insertion:] It is well known that the skin of fur animals are more valuable in profiting as they are called fuller [health]

[For readability Darwin's horizontal and vertical crossed lines are left undeleted]

In plants, I believe scarcely any Botanist doubts that the individual of the same species become smaller, more hairy & with white r brighter coloured flowers at great heights. See Back

(a) Several cases also, are on record of the same individual plant or of all their seedlings changing within the end of selection in a few generations changing to that of their flower, when brought from their native home into our gardens*(c). I have not quoted instances in regard to the changes in insects & plants in ascending mountains, for naturalists differ so greatly in all such cases, what forms to consider species & what varieties.—

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*(a) Quoted by Bronn. Gesichte der Natur B. 2. s. 96.—

and Mr. Wollaston on the Variation of Species p 39-41.

*(b) Ib. p 57-64.—

*(c) Dr. Hooker on the Climate & Vegetation of the Sikkim Himalaya p 49. in regard to a Rhododendron; & see, also, Mr. H. C. Watson's account of the Azorean Myosotis. Azorean plants Myosotis

*(z) From the character of the species, not varieties, inhabiting very dry districts, as the Galapagos archipelago,—the deserts of Peru & Northern Patagonia, it would appear as if dampness was an element in the bright colouring of birds & insects.—

(a) Moquin-Tandon on same species getting more fleshy leaves near sea coast —

(zz) Perhaps allude to Hooker to show how easily one may fall into mistake.

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D text)

Cold seems to lessen the intensity of the colours of flowers, as seem is asserted to be the case with some on high mountains, & as was has been observed by the Dutch cultivators with their Hyacinths.*(E) (*(E) Moquin Tandon Elements de Teratologie p. 42)

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: moreover Dr Hooker after tabulating some Alpine floras does not find that in truly alpine species the proportion of woolly plants to be large. He is inclined to believe that dryness has a stronger tendency to produce hairs on plants.*( *see the Moquin Tandon gives, also, several facts in corroboration of the same view. Ch. 2.- p. 65)

Most of these variations are apparently of no service to the organisms thus characterised, & therefore cannot hardly have not having been done to affected by selection, must may be wholly attributed to im the immediate action of the conditions of existence. Small & unimportant as are the modifications, it deserves

[in margin, pencil note:] can not due to selection

notice, that they almost invariably tend in the same direction with the characteristic differences of the species peculiar to the districts under comparison. Thus, how incomparably more beautifully coloured are the sea-shells of the Tropics compared with those of the cooler temperate regions. It is, also, well known that shells confined to great depths are almost colourless. like the variation ranging Alpine beetles species of Coleoptera are generally dark-coloured; & Mr. Wollaston expressly states as every collector must have noticed that littoral beetles confined to the sea-coast are generally "lurid-testaceous or pale brassy". Mr Plant [text excised] shells

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(Ch 7 Immediate action of external causes)

Species of plants living near the sea often frequently have fleshy leaves; those of dry & hot countries woolly leaves; those in tropical regions brilliantly coloured flowers. Arctic quadrupeds are thickly clothed with fur. Birds The species of birds, which are confined to the interior of continents, according to Mr. Gould, are more beautifully coloured than those which inhabit the coasts & adjoining islands.

In all these cases, the species, which are only according to our views are only strongly marked varieties, are naturally affected in the same manner, but in a stronger degree, as the slighted forms admitted by naturalists to be mere varieties.

If Buckman did not use selection, here allude to his facts as strongest evidence of direct action of food & cultivation.

(In some cases the action of external causes, which I have called immediate, from its influencing apparently without selection, all the individuals exposed to it,

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(Ch 7 Immediate action of condition)

seems indirect in its influence; by which, I mean, that very different conditions will produce the same result. Thus Dr. Harvey, the highest possible authority on sea-weeds, says*(Sea-side Book 1849) p. 66) that the Fucus vesiculosus ha appear at the Canary Islands, where the heat is too great for it, appears under a nearly similar form, as in the Baltic where it is injured by fresh the brackish water & mud; & he adds that no one "would be prepared for the fact that the heat of the tropical sea would exercise the same transforming influence power on a particular plant as the mud & fresh-water of a colder climate." In some not a few other cases, also, it would appear that an organism presents a nearly similar range of variation variation under whatever condition it is exposed: thus to give a very trifling instance, the common Polygala has blue, white & purple flowers in the cold humid island of Faröe*a in 62° in England & southern Europe? [pencil insertion:] Juncus & Del[illeg] in Italy certainly man's flora Sadima The Juncus bufonius which ranges from the arctic regions to the equator "in every region seems to present the same variations in its size & branching."*(b) These & similar facts cases, which I believe to be not common, though Dr. Hooker thinks a good many could be collected,

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*(a) Landt, Description of Feroe p. 180 see Herbert in Hort. Journal vol I p 48 (?) or ask Bentham Lat. of Zante.

*(b) D. Don on Indian Junci in Linn. Transactions vol. 18. p. 324.

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of which I have noticed of a few few cases,

lead us back to the perplexing case facts of polymorphous genera species & genera, discussed in the fourth chapter; they show us how ignorant we are on the subject of variation, & how pre prepotent an influence, the organisation of the species has on the causes, whatever they may be, of variation.

Upon the whole, I think, we must attribute some effect to the immediate action of external conditions; but I am inclined to think it is very very little. Innumerable instances could be given of organisms of all kinds exposed to an immense range of climatal & other conditions,*(a) & yet not varying in the least, & although, as Mr. Wollaston has remarked, we ought by no means to infer because these causes have no influence on one species, they will not have none on another; yet I think we may to a certain extent be guided by their many facts their frequency of such cases of non-variation. As I consider those forms which are considered ranked by most Naturalists as independently created species, as only strongly

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p. 9 (v) Perhaps one of the most striking cases, is that given by Göppert (Wiegmann's Archiv fur Naturgesch. 1837 p. 210) of unaltered species growing on hot soil above burning coal; & other similar cases given by Humboldt in regard to certain grasses on the edges of hot-spring springs.

Many plants have eno enormous ranges (see Hooker Introduct. New Zealand Flora p. x) & remain unaltered; some range from the base of the Himalaya & other mountains up to an immense height. A land-shell, the Nanina vesicula ranges from the hot plains of India up to 10,000 feet (Huttons Chronology of Creation p. 202) on the Himalaya, where a Toad has an immense range (Hooker Himalayan Journals vol. 2. p. 96). — For wide range of insects see Mr. Wollaston's excellent discussion, p. 29-31 in his Variation of Species.— It would be easy to accumulate innumerable examples.—

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marked varieties, the high degree of generality of the fact, that the tropical & temperate, & temperate & arctic zones, are inhabited by species, often closely allied, of the same genera, as strongly confirmatory of the view, that climatal conditions have no great effect influence on organisation; but to those, who look at species as independently created, these latter facts will have no weight.

(Acclimatisation. —Though climatal conditions may have no great influence on organisation or visible structure, yet it is notorious that the great majority of organic beings are adapted, within moderately narrow limits, to the climate of the regions which they inhabit. When, therefore, a Naturalist meets an animal with are exclude a very wide range, for instance the Puma in the reeking hot forests of central America, on the dry deserts of Patagonia, in the damp cold woods of northern Tierra del Fuego & up to the limits of eternal snow on the Cordillera, he is much surprised; for he is accustomed to meet for instance, one species confined one cat adapted to the Tropics, another to the temperate & another to the cold regions; his surprise is, also, increased, from falsely attributing (as I believe) attributing far too much weight

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(Ch 7. Indirect action Acclimatisation)

to the relations of between climate & visible structure; climatal conditions are manifest; but the more important conditions determining each organisms creature's power of getting food & escaping dangers are obscure in the highest degree.

Nor must we overrate the degree of adaptation in the constitution of each living being to its counts the climate of its own restricted home: when a new plant is introduced from a foreign land, until actual trial we cannot closely tell what range of climate it will endure. Even plants peculiar confined to certain islands, & which could have ranged out of these into any other climate (within can look to past geological agreeable positively into perfection) have never ranged, as far as we know beyond the narrow confines of their home, are found to endure very different climates: look at the Snowberry tree (Chiococca racemosa) how difficult to eradicate from our shrubberies, who would have ever supposed that it was had been naturally confined to the West Indian islands? (a)

[For readability Darwin's horizontal and vertical crossed lines are left undeleted]

Those who think each species created, as we now see it, will must we say that such island plants were created for the prospective chance of the island becoming joined to the mainland & then the plants in question spreading?—

Nevertheless there can be no question that very many, probably most organic beings are pretty closely adapted to their own & no other climate; & if the species

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Baleanic Box — Myosotis azoica.— flowering in March if mine.—

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(Ch 7. D Acclimatisation)

of the same genus are descendants from one common parent, they many of them must in the course of ages have become very differently acclimatised. accustomed to very different climates. Is this possible? I think the following facts, though few from the nature of the case, show that plants at least do become in some degree acclimatised. Dr Hooker states (Flora of New Zealand Introduct. p. xi.) that he has found a great difference in the hardiness of individuals of several Himalayan plants, depending upon the altitude height at which the seeds were gathered: he instances seedling Pines, which were hardy taken at the height of from 12,000 feet, & tender were hardy in England, whilst those from 10,000 feet they were tender; & so there is a great difference with the scarlet Rhododendron arboreum according to the height at which the seeds were have been collected.

Mr. Thwaites, the curator of the Botanic Garden at Ceylon, whose accuracy & knowl is well known, writes to me, that he finds "that individuals of the same species become are acclimatised to different elevations,—becoming being more & more impatient of cultivation at any station, according as they have been transported to this it, from stations of greater & greater altitude." Again Mr. H. C. Watson who has cultivated plants apparently a variety of a British Lysimachia by himself brought home from the Azores, which are common to Britain, finds that the Coz[illeg]individuals are & found it was decidedly tender.*(P) (*(P) Phytologist. vol 2. p. 976.)

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(Ch 7. Acclimatisation)

(I think, also, that there can be little doubt that the varieties & sub-varieties of our domestic animals & plants become in a slight, though very slight degree, acclimatised each to its home: I infer this from the incessant caution incessantly given in works ancient & modem of agriculture, in all countries, even by in the old Chinese Encyclopedias, not hastily rashly to change the breed of any animal or race of a plant in any from one to another district, more especially in wild mountainous districts.

[For readability Darwin's horizontal and vertical crossed lines are left undeleted]

Many cases are on record of horses, for instance, introduced from different countries with a new one, during war, tendency the climate better or worse in accordance with that from which they were have been brought. [in margin:] Royle

Different dogs have extremely different capacities for standing heat, but then their probable origin from distinct species renders this case of lit no value. No one, I presume doubts that the negro & Laplander have very different constitutions in regard to climate.

(Again we have some cases instances, but here also from the nature of the case but few are also known, of animals naturally extending their range, though we do not know how far the individuals actually become acclimatised to their new homes: thus Audubon gives several instances of Birds, which undoubtedly (during late years

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(a) text/ The horses from Algiers stood the climate of the Crimea better than those of Europe: Merino-sheep from the Cape of Good Hope "are far better adapted" to India than the same breed from En England*(a): The cactus introduced into India from Canton, Manilla, Mauritius & the Kew Botanic gardens were undistinguishable to the eye, but the Cochineal insect perceives a great difference, for it will flourish only on the Indian plants, supposed to have been formerly imported by the Portuguese.*(B)

(*a Royle Productive Resources of India, p. 153.) (*B. Id. p. 59)

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have extended their range much further northward during late years in the United States.*(a) Thus, also, there can be little doubt that owing to the introduction of cattle, a vulture (Cathartes aura atratus) in S. America now ranges many hundred miles further south than it originally did three centuries ago.*(b) The innumerable instances of plants, not cultivated by man, & of some few animals insects for instance not domesticated, which have been naturalised through his agency in so in many countries under wrong different climates differing in some degree from the native climate, show clearly that organic beings can adapt themselves, whether or not becoming acclimatised, to somewhat different climatal new conditions. Look at the common mouse & rat which have run wild on the hottest & dryest volcanic & coral islets under the equator, & in Faroe in Faroe in the north & at the Falkland Islands in the south; it is opposed to all probability that these species had aboriginally nearly so wide a climatal range. The Fallow-deer is almostferal in Barbuda in the West Indies islands, & can live on the shores of the Baltic; but it is superfluous to give other instances.—

These facts lead me to believe, that many organic beings by slowly extending their range, where can could become acclimatised. Whether the acclimatisation is

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 *Zoology of the Voyage of the Beagle p. 7. The Rio Negro is about 500 miles south of Monte Video, where according to tradition they did not formerly exist, having come there from still further north.—

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In Portfolio "Instinct" some excellent facts from Bachman on change of ranges in N. American Birds even Pelidna.

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Kalm 1/292 The maize thieves (icterus) & several sorts of squirrels have increased owing to the greater cultivation of maize. 1/294. Codfish were formerly never caught at Cape Hinlopen, but now they are numerous there

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253

àAcclimatisation.—

Bachman tells me in Audubon there is most curious history of first appearance of the S. American Pipra Flycatcher, which is now becoming common— likewise of the Hirundo fulva (added by Audubon in Appendix) showing what changes are taking place & how birds are extending their ranges even migratory birds, like swallows.

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Of migrations of birds he mentioned many most curious case.— the birds seem to follow narrow bands, certain kinds as gallinules taking the low country near coast & others the mountains, & this

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254 See Silliman's Journal 1837. Paper by Bachman.

appearing to remain about a fortnight that is succession of birds.—in some species as Tanagra males come first & then females in flocks as in English nightingales.—other birds (& this seems common kind migration of America) migrate singly flying few miles every day & generally by night—one bird which is strictly diurnal, migrates singly by night.—others in flocks, kind of migration quite different in species of same genus, these birds seem clearly directed by kind of country; the Muscicapa solitaria stay about a fortnight in one particular part of country, like White of Selborne Rock Ouzels.—If the line or bands of country (These facts show the normal condition of migration).

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Silliman's Jour. vol. 19 p. 357. Describes the first appearance at Union in Maine, in the of a new kind of swallow, in the first 5 years there were about 50. At Saratoga they arrived in 1828, they have since increased rapidly, so that at in 1831 they were computed at some hundreds. Is not this spreading North.

[Steel, J. W. Swallows: Extract of a letter from Dr. J. W. Steel, of Saratoga Springs, to the Editor, dated Dec., 9, 1830. American Journal of Science and Arts 19: 356-7.]

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(Ch. 7 Acclimatisation)

effected by mere habit, or by the se natural selection of var individuals born with a [illeg]constitution, due as [illeg] was found to say from our ignorance to chance, fitted either to greater heat or cold, it is impossible to say: probably both actions concur. The spreading of any organism, in those cases in which there is no physical barrier, will depend, mainly, on the other whi the nature of the other inhabitants, whether that is whether there be any place open for it which it can seize in the polity of nature. If there be such place to it it would appear that animals & plants will, the organism would sometimes extend its their range, even although the climatal conditions ha are in some considerable degree unfavourable to it them, as we see with the dwarfed Elephant reduced in size in India north of Lat; & with the Capercailzie*, reduced in size, in northern Scandinavia; & with the dwarfed trees in the northern parts of Scotland & the United States. In the second placeBut the spreading will, also, depend upon how closely the organism has become rigidly acclimatised to the conditions of its native home. Nearly all our domestic animals & some plants have great climatal flexibility of organisation, as we see in their domestication cultivation & in their becoming feral state of some under many such different climates; in them & perhaps more especially & in their their generally retaining perfect fertility under sudden & great changes of climate.

Although we are in many cases we do not know

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*L. Lloyd Field Sports of the N. of Europe Vol I p. 284 in Lapland this bird seldom weighs more than 9 or 10 pounds, whereas in the southern parts of Sweden it not seldom exceeds 17 pounds in weight.—

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what were the parent forms & what its their natural ranges, or how many aboriginally distinct species are now blended together in our domestic races; yet if we look at the whole body of them our domestic productions — or even if for instance we run through the shorter catalogue of the our domesticated Birds—there can be no doubt that they inhabit under incomparably live under a much greater range of climatal adaptation diversity of climate condition than do an equal number of organisms taken at hap-hazard in a state of nature. The arguments given towards the close of our second Chapter have convinced me that our domestic productions were not aboriginally selected from having this constitutional flexibility quality, though doubtless they are far more useful from now having possessing it; half-civilised man could neither know, nor would he care, whether the animal which he was taming or the plant which he was cultivating possessed was so thus constituted; he would not care for this more than did the Laplander when he domesticated the Rein-deer, or the inhabitants of Arctic or Persia,the hot deserts of the East when he domesticated the Camel. Hence then, I conclude, from the very general, though as we have just seen, not

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universal climatal constitutional flexibility of our domestic beings productions, either either that a organisms in a state of nature possess this same quality possess far more generally than we should expect from their natural ranges, considerable constitutional flexibil or that the simple act of domestication placing deciding an organism being out of its natural condition act of domestication gives this constitutional capacity for bearing climatal changes in a high-degree. I suspect that this is the case; & if it be so, that is if an, I cannot avoid doubting It may be doubted, whether if the wild single or multiple parent-form or multiple parent-forms of the Horse, the goat the Fowl &c the maize, tobacco, rice, wheat &c were suddenly carried from their wild native state into the various climates under which the domestic races now flourish, they not would be prolific & healthy. If this doubt be correct & however, if an animal organic being subjected to domestication or change of some kind, has its constitutional constitution adaptation to special climate so far broken down, that it can acquires a general degree of flexibility, then we can perhaps understand a statement generalisation fact insisted on by M. Alph. De Candolle, which long appeared to me very strange;—namely that with the progress of knowledge, species of plants in a state of tend nature are found to divide themselves into two opposed categories, "les unes locales et ordinairement tres locales, les autres très repandues."*(*Geographic Botanique p. 484)

For according to this notion, as soon as a plant begins to spread, it would be in predicament of a domesticated production & would gain flexibility of organization & might spread very far.—

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Col. Sykes. Fowl from India, native home, bred readily in this country—screw loose—we must say that act of domestication by itself in a being never transported to other country gives flexibility to endure climate!

(a) A screw loose—this fact of when adapted & enabled to beat two sets of organisms is enabled to beat many more sets, must be far more important element —yet above must come into play.

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Finally then I conclude that all animal organism being being tends slowly to spread (where no physical most animals & plants are capable of spreading beyond their present confines, when no physical barrier is opposed to their progress); under favourable beyond [illeg] present confines; others being checked by; the main & general check being the presence of other & better adapted organic beings; & secondly the second being its but that it is likewise checked by being become a second check being their native acclimatisation to other native homes but that this better check may be overcome by habit & natural selection; & that when overcome, the being tends to gain a general degree of flexibility of organisation, allowing it to spread very widely, as far as climate is concerned; its its means of obtaining food & escaping danger will permit it being then the sole but great powerful checks to progress extension. On this view, such facts as the former existence of a rhinoceros & elephant adapted to a glacial climate—the wide extension of man himself,—of his domestic ani productions & of those accidentally transported by him —are not exceptions to a general law: it is only that these animals have lost their special acclimatisation & have regained their normal constitutional flexibility.

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Effects of use & disuse on structure.—That constant action will increase the size of a part & that this increase becomes hereditary, I think can hardly be doubted from the facts given in the first chapter for instance the size of the mammae in our cattle cows & of [illeg]goats when habitually milked, the more muscular stomach of owls & if gulls fed on vegetable matter; & the great weight of the bones of the feet & legs of the domestic duck &c. On the other hand from disuse parts decrease in size, as we see in the wings of the duck & of the Cochin China fowl. (?) Nor is this at all surprising because as we have seen parts become atrophied, when not used from any accident, as the optic nerve in an injured eye visibly more developed, or atrophied, from can from accidents & operations, during the life of an individual.

(In a state of nature, the same variety cannot be observed during very many generations; the conditions of existence when they change change most slowly; hence we & if a sensible modification did occur in any form, that form would naturally be considered as a distinct species, hence we cannot perceive recognise the effects of use & disuse in varieties in a state of nature. But as species are if we look at species, as only strongly

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marked varieties, we frequently meet with structure analogous to that produced resulting from disuse under domestication. Thus the great logger-headed Duck*(*Micropterus brachypterus Eyton. Zoology of Voyage of Beagle. p. 136.) of Tierra del Fuego, which so much surprised the old voyagers, & which I have often watched, cannot use its wings more than a fat Aylesbury duck, & is under any extremity incapable of flight. Feeding, as it chiefly does in the great beds of floating kelp, & never in it does not require wings to escape from danger, to which it would hardly be more exposed, than the ocean-haunting Penguins. which use their wings, only not since for flight but as fins, The islands of Mauritius, Bourbon, Rodriguez, the three is isla of north, south & middle New Zealand, & of Philip all have had birds, belonging to several orders incapable of flight; & when we remember that no beast of prey inhabited these islands, & that ground-feeding birds usually take flight only to escape dangers, I should attribute, their almost wingless state to disuse.

[21a]

Owen

N. Zealand Bird — general sketch of — how many types. How close Apteryx to Struthers as close as most distinct other Struthionidæ. Ch 7

[21av]

Nov 21/57 conversation with Owen I think 3 types Rallidæ—Aptornis either distinct or a Parrot—& Dinordinæ, which includes Apteryx —

If there could be winged Dinordinæ—these might have come by flight—If Dinordinæ close to Rallidæ or other winged Birds then perhaps always wingless—Though I should think even Struthionidæ were once winged.—

[21a2]

& they can escape danger by their fleetness, & in close quarters by their dangerous kicks, quite as well as any small quadruped, so though here agains disuse together with the increasing weight of body their bodies may well have come into play rendered them incapable of flight.

The fact of so many birds with imperfect wings inhabiting oceanic islands, naturally leads us to

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the disuse. In New Zealand, the wingl birds incapable of flight, belong, as we know from Prof. Owens wonderful discoveries, to 3 or 4 groups very different orders; & therefore I should infer that at least so many birds had colonised these islands ages ago, had become [illeg] almost wingless from disuse, & had branched out & since given birth to the new score of birds in this state now inhabiting these islands. On account of as the apteryx belongs But as several of these belong to the ostrich family it may be rather doubted whether th these became wingless supposed that one at least of the original colonists, arrived, we know not how, at these islands in an already almost wingless state. But in regard to the other almost wingless birds of New Zealand & of the inhabiting maintain other specified islands, it seems to me probable that they lost they arrived by flight & that their wings have since became almost atrophied from disuse in their new & protected homes. With respect to In that ostriches family which inhabit continents & great islands, as we see that they

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Mr. Wollaston's (Insecta Maderensia p. xii. and Variation of Species, p. 82 to 87.        ) remarkable discovery of the frequently apterous condition of the Beetles at Madeira; for no less than 200 species out of the 550 coleopterous inhabitants of this island, have their wings in various stages of reduction & are incapable of flight; & this which undoubtedly is a more wonderfully large proportion. (a)

[For readability the horizontal and vertical crosses are left undeleted]

Moreover Mr Wollaston has enumerated 17 genera, which are usually have winged species in other parts of the world, but wingless in Madeira; & 29 endemic genera, that is genera actually or those strictly wholly confined to the island, no less than 23 have all their species apterous incapable of flight! Still more remarkable is Mr. Wollaston's conviction, & no one can be a more capable judge, that some few of the very same species, common to Europe & Madeira, are wingless on this island & winged on the continent; & he gives full details in regard to three of them. Here, then, I may add we have another case of varieties in a particular locality marking the endemic species, supposed by Mr Wollaston and others to have been independently sta created;which are exposed to the same conditions; or as I should look at it the case we here have permanent & strongly marked varieties, called species, very naturally possessing having the same character as with the less-strongly marked forms, recognised called by naturalists

[22v]

(a) The more wonderful, as winged Beetles would originally during the whole existence of Madeira as an island have had a better chance of getting there than aboriginally wingless species; just on the same principle that winged many European birds inhabit have by their wings reached Madeira; & that the only mamifers mammals existing there are the winged Bats. We see clearly the tendency in the beetles of Madeira to be wingless in the fact mentioned by Mr. Wollaston, that 17 specified genera here have have wingless species, which genera usually have winged species in other parts of the world. Moreover of the

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in some varieties.

In regard to the origin of the apterous condition of the Madeiran coleoptera; as Mr. Wollaston repeatedly remarks, that the Beetles on the more exposed rocks lie concealed during the almost incessant winds, & immediately appear in swarm numbers, when the winds lull & the sun shines, something may, perhaps, be attributed to the mere disuse of their wings just as with th the males of the silk-moth. But I am inclined here to lay far more stress on the principle of selection with or rather with its antagonist action of destruction. Beetles from not being powerful flyers are very liable to be blown out to sea, as I have repeatedly witnessed, & this would naturally happen far oftener on a small island than on a continent; therefore on an island active individuals with a strong tendency to use its their wings would be oftener destroyed, & a sluggish individuals with its their wings feathers reduced in size, however little the difference might be, would in the course of ages be oftener preserved, & would leave offspring with the same inherited tendency; & this process ultimately, through continued selection, might render the beetles quite safe from being blown to sea, by rendering its their wings either rudimentary. or suddenly quite atrophied aborted. As the danger would be obviously greater, in the smaller & more exposed the islets, I have ascertained through Mr. Wollaston's kindness

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that on the Dezertas, a mountainous rock near Madeira, four miles long & about three-quarters in breadth, there are there are 54 Beetles; live & that of these, 26 are winged & 28 wingless, which is a proportion one-fourth more wingless larger, less insects than the Dezertas ought to have possessed had in accordance with the proportions of the winged & wingless coleoptera in the whole archipelago.*(a) On From the Salvages, a rock rocky islet little rock, between Madeira & the Canary islands, six Beetles are known to Mr. Wollaston, & four of these are apterous: at Kerguelen island, Dr. Hooker found only one beetle & one moth, & both are were apterous.

Any beetles which were from not being a ground-feeder or which naturally absolutely required wings for any purpose, would on the principle above explained run great risk of utter extinction; without indeed the its conditions of its life were so very highly favourable to it in Madeira that it could bear great occasional loss from being blown to sea. Now one of the most remarkable features in the entomology of Madeira, strongly insisted on by Mr. Wollaston (Insecta Maderensia p. x) is the entire absence or extreme rarity of certain whole Families &

[24v]

In working out the proportions, the insects believed by Mr. Wollaston to have been introduced by the agency of man have been left out on both sides.—On the Dezertas, however, the number was only three. If I had contrasted the Beetles on the larger island of Madeira itself, with those of on the Dezertas alone, the proportions would probably have been greater than that given in the text.

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(Ch. 7 Disuse)

(On the other hand, in those orders classes of insects which are not ground-feeders & are rapid & powerful flyers, this very power might save them from utter destruction, by allowing them to battle against the wind. And

Such insects might even have their wings increased enlarged by natural selection; and Mr.

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genera of Coleoptera, which abound in species on the mainland of Europe under a similar climate: & of these deficient groups it is well worthy of remark that a large majority include the greatest flyers *amongst in the whole order of coleoptera.

On the other hand powerful & habitual rapid & habitual flyers belonging to other orders of insects might escape destruction in any extreme degree by battling with the wind; & even by natural selection have their wings increased in size, & MrWollaston (Variation of Species p. 87) says he is by no means certain that this is not actually the case with the Lepidoptera & some flower-feeding beetles, which if they are to live at all, must have wings & use them. Hence I can see no difficulty in two directly opposite processes going at on the same time with different members of the same great class; some having their wings reduced by selection & disuse, others having them increased, —just as Pigeon Fanciers during the few last centuries have decreased & increased the beak length of beak of the tumbler & carrier pigeons, both derived from the same stock.

The turning point will have be been when the an insect first arrived on the island, whether, according to the nature of its food, its individual numbers would withstand be were increased by its flying less or more.— less & worse & so running less chance of destruction being blown to sea; or flying better so as to conquer the winds.)

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great genera of Coleoptera, which abound in species on the mainland of Europe under a similar climate. Thus to take the Families alone of of Cicindelidæ there is not one species; of the following enormous fossils great groups only one in each up to the present day, as I was informed by Mr. Wollaston, has been discovered, namely of the in Buprestidæ, Elateridæ, thalerophagous Lamellicorns, Telephoridæ, Oedemeridæ, Silphidæ (not one Silpha or [illeg]) & Pselaphidæ.

No one but an entomological collector will fully appreciate this most remarkable fact. In considering this list it occurred to me that these very deficient Families were those greatest flyer which, which I was led to do by Mr Wollaston it occurred to me that these very Families (the remark does not apply to all the genera) were exactly those which from their habits of life most often do actually use their wings far more than other Coleoptera: accordingly I enquired from Mr. Wollaston whether this was not the case, & he has gone through the whole list all &, with the exception of the Pselaphidæ, says that undoubtedly this is the case. it is so. Therefore I think we may with some safety conclude that a vast majority of those Beetles, of which the habits of which did not allow them to subsist without wings have been exterminated & therefore did not allow them to become apterous by disuse through selection & disuse have been wholly exterminated: & this conclusion supports the former one on the origin of the apterous species.)

[25v]

require wings, support the view that

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(Ch. 7 Disuse)

Such, I believe, to be the explanation of the conditions of the wings of the insects on Madeira; but it must be plainly confessed, that doubt is thrown on it, from the fact, discussed by Mr. Westwood *that in many parts of the world, there are insects belonging to various orders, of which individuals may be taken either winged or perfectly apterous; of this fact the common Bed-bug is a well known instance.

It has been thought that the wings are developed during hot seasons, but the evidence seems to me hardly sufficient. But The case facts anyhow plainly show that there is something in regard to the wings of insects, which we do not in the least understand.

[in pencil:] Mr Walich says not disuse, else Tarsi when present wd be loss

Loss of tarsi.—

We will now turn to another organ somewhat analogous & [curious]case: Kirby has remarked (Introduction to Entomology vol. 3. p. 337) that in the in certain Scarabæidæ, (dung-feeding beetles) the anterior tarsi of the males are generally broken off: he examined seventeen specimens in his own collection "& not a single one had a relic of the anterior tarsi"; (a) I wd remember formerly, when largely collecting in this Family, having made the same observation; & Mr. F. Smith of the British museum tells me that he, also, has observed it. This loss of frequent, & almost habitual loss of a portion of the

[26v]

Modern Classification of Insects. Vol. See Also in the Mr. Wollaston Variation of Species p. 43-45.—

[26v]

(a)

; & in Onitis apelles they are so rarely present, that this beetl the tarsi in this beetle have been supposed by some authors not to exist.

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front limbs can hardly be counted with their habits of life, as far as of the males is not common to all the genera, having the same general habits, for it is not observed in Copris or Onthophagus.*(zz)

If mutilation are were inheritable, as many authors believe,—if cutting off a dog's or cat's tail tended to make it them produce tailess offspring,—then we might have expected to have found find some result from this almost habitual loss of the tarsi in the beetles; but I cannot believe in mutilation being inherited thus. Nevertheless so constant a loss must clearly shows that the anterior tarsi are of not much service to the insect & therefore probably are not much used; & disuse, I do not doubt are inherited causes atrophy & is inherited. Now in the above men genus Onitis above referred to & likewise in Phanaeus,*(a) one members of the Scarabæidæ, the tarsi are "very slender & minute", & may be said to be quite rudimentary; indeed in the Brit Mus I could not find any specimen of Phanæus with tarsi, & in another genus, Ateuchus, Mr Waterhouse tells me that he believes, after repeated examination, (which includes the great sacred beetle of the Old Ægyptians) it is well known that the are tarsi of the front legs are absolutely deficient.*(a)

Have the loss very small size or less therefore of the tarsi more than beetle

Hence I am inclined to attribute the very small size or loss of the tarsi in these beetles, wholly to disuse.

[27v]

*a M. Brullé (in Annal. des Science. Nat. 2 series Zoolog. Tom 8. p. 284) asserts that in Phanæus the males are deprived of tarsi, whereas the females almost always have them. He adds that in Onitis, the females of some of the species have tarsi, whilst in other species neither the males or females have them.

I do not know whether M. Brullé was aware of the frequent accidental loss of the tarsi in several other coprophagous genera.—

 *zz I do not suppose that the tarsi are lost by the males fighting: at least in Lethrus, in which the males are known to fight furiously, the tarsi were quite perfect.—

[27v]

 *It would be easy to bring forward cases of the affected atrophy or entire disappearance of parts apparently from disuse; but as these occur normally in all the individuals of the species, & as I cannot illustrate them by analogous variation losses in certain merely in individuals or varieties, I have not given them in the text.

The Many api parasitic Crustaceans have their limbs atrophied when attached to for life to the in fishes. on which they In another totally distinct Kingdom, there is a striking case in as much as it occurs in nearly full-grown individuals in the Pholas lamellata; which this shell has been described as a distinct species, but has been shown by Mr. W. Clark (Annals & Mag. of Nat. History vol 5. 1850. p. 12: see also Dr. Fleming's British Animals) to be the half grown shell animal of Pholadidea papyracea, which after it has domed its shell, does not any longer require its large muscular foot for boring, & consequently the whole large muscular foot is absorbed & disappears. "depauperated & finally obliterated."—

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(Ch. 7. Disuse)

Blindness. (I have one more class of facts of the same nature to bring forward. It is well known that moles & some allied genera owing to their subterranean habits have either excessively very small yet perfect eyes, (a) or, eyes buried excessively minute, & buried under fairly covered over by the hairy skin, so that if they have any vision at all, it must be confined to the dimmest perception of mere light.—The burrowing Aspalax, (a subterranean Rodent & therefore belonging to another order of animals) is in the same predicament; its eye being excessively minute & covered by not only the by skin, but by a tendinous expansion. Now in S. America there is a very common rodent, the Tucu-tucu (Ctenomys Braziliensis), more subterranean in its habits even than the mole: I heard of a Spaniard who had often caught them, & without my saying anything to him making any remark, he stated that "invariably very many are found blind": he procured me some specimens, & one of which I kept alive, & one of them was evidently stone-blind; I preserved it in spirits & Mr. Reid dissected the eye, & found that the blindness had apparently been caused by inflammation of the nictitating membrane. As blindness tends to

[28v]

(a) (The opening eyelid of the mole in the as in European mole, in which the eyelids are hidden under thick fur, & are being one-third of the size of the head of a middle-sized pin;)

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(Ch. 7. Disuse)

cause atrophy & as diseases of the eye are believed to be strongly hereditary (especially with horses), I can see no difficulty in believing that the Tucutuco eyes of the Tucutuco might be reduced by disuse & disease to the state of those of the As Aspalax: yet as disease inflammation of the eyes must be injurious to this any animal, & as it can wants its eyes these organs vary little & it is by no means improbable that, the Aspalax can live without live in its blind state, it may well have been that the absolute closing of its eyes was effected by the continued selection of smaller & smaller eyes & more closely shut eyelids.—

It is well known that in the deep caves of Styria there are many blind insects, & Crustacea (⸮)arachnidæ & a reptile the Proteus: in the caves of Kentucky there are, also, blind insects crustaceans, fish, & a Rat. (a) Now as the existence of useless eyes would could hardly be injurious to these animals, I should attribute their blindness to simple disuse.

Although it is trenching on a distinct subject, I may remark, that nearly the many of the cave animals of the

[29v]

(a) The various stages of abortion of the eyes in these Kentucky animals is very curious: some have no trace of an eye, some have a rudiment, & the crustacean has the footstalk for the eye without any the organ,—it has the stand for the telescope without the instrument.

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(Ch. 7. Disuse)

cases of Europe & N. America, though exposed to very do closely similar conditions of existence, are many most of them except in their blindness very unlike little allied. (Transact. Entomolog. Soc      )

According to my views, these animals were not created in their respective caves, but American animals must have got into the an Kentucky caves, & European animals into those of Styria, slowly penetrating, century after century into the profounder abysses, & gradually now in the case at least of America, & the have become blind by disuse: & they would, also, become modified in any other way, through selection gradually fitting them for their strange [in pencil:]new new & dark homes. [in pencil:]as they would in a way with the [2 words illeg]Now in regard to the Kentucky caves, Prof. Dana informs me that the Crustacean is

[in pencil:] Fish & Rat –

In the case of Syvia. Some of the forms are straight & are only varieties of European insect;but I have failed in finding out the affinities of the insect, but one or two are even thought to be only varieties of European insects.—

Protean has American & European species

Look in Dict. class for range of each genus & write to Dana to ask.

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In the discussion on the Madeiran insects, I remarked that it was quite possible that natural selection might at the same time be increasing enlarging or reducing the wings of different insects of the same group class. In the caves of Kentucky I think we have evidence of an something analogous in regard to the eyes of the animals; the contest, however, being here between selection enlarging & disuse alone reducing these organs. The blind cave Rat, instead of having minute rudimentary or no eyes, has eyes of an immense size; & Prof. Silliman Jun. who kept this animal alive, thought that after a period it acquired & when accustomed to the light, it acquired some slight degree of vision. Now if we may suppose that this animal did not habitually live in the dimmest utterly dark parts of the caverns, we may suppose th according to our principles, that the individuals with infinitesimally larger eyes & a more sensitive optic nerve had been continually selected, until some American rat from the outside world, had been converted into this strange inhabitant of darkness, with its [large] eyes, blue fur & long moustaches?

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(Ch. 7. Disuse)

(In the depths of the ocean, & in deep & dark wells some Crustaceans as Calocaris & Niphargus are blind.*

[in pencil:] Pecten??

Now though I am not aware that any Fish inhabiting very deep water is normally blind, yet it seems to bear on the blindness of above facts, that the Gadus lota (Mr. Prof. Jurine in Mem. de la Soc. d'Hist. Nat de Geneve Tom 3. p. 149. 154) at the depth of 100 fathoms & [illeg] is often totally blind; & has its air-bladder frequently atrophied, often accompanied by total blindness.

On the other hand, just as in the Kentucky cases we have some animals blind & & another it has been "remarked that fishes which habitually descend to great depths in the ocean have large eyes". (Sir John Richardson Encyclop. Brit. art. Fish p 219) And one most remarkable fact is on record, which is worth giving, though of a most perplexing nature. M. Eudes-Deslongchamps gives with great detail two cases. (Mem de la Soc.Linn. de Normandie vol. 5 1835. p. 47, and vol 7. 1842) of eels taken from deep wells about 100 feet in depth, which had their eyes of immense size, so that their upper jaw in consequence projected over the lower. But here comes the remarkable fact the first specimen was shown to Agassiz, & he

[32v]

 *E. Forbes. Report Brit. Assoc. 1850 p. 254.

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(Ch. 7. Disuse)

thought it was specifically identical with the common Eel. One of the wells was within the precincts of a prison; & it seems impossible to conjecture how the eel got in; & it seems, moreover, quite incredible that such an alteration could have supervened during one generation: it comes is, also, most improbable that there should be a breed race of subterranean eels, for, I believe it is well established that the eel invariably breeds in the sea. Surrounded with difficulty as this case is, we apparently have in the [illeg] state of the eyes of fish its great depth in lakes & wells & large eyes of these eels, & in the blind Gadus from the deep parts of the lake Leman, a parallel series of case to the opposite condition of the eyes of the Kentucky cave-fish, crustaceans &c the Kentucky cases to that in contrast contrasted with the large eyes of the cave-Rat. in the [Kentucky caves]

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(Ch. 7. Correlation of growth)

Correlation of growth.— In the first chapter I briefly alluded to several laws, most obsu dimly seen, which appearing to govern that variability. on which selection can add up &c. These laws are most imperfectly known; & I will here recapitulate them, adding a few remarks, more especially in regard to the a comparison of the structure of those forms, recognised as varieties, & species those which are generally supposed to have been formed by distinct acts of creation. Physiologists admit a principle, which they have called "nisus formaticus", which repairs, often in a wonderful manner, accidental injuries; & I think we may infer, that if any part were greatly increased or altered in form by continued selection, this "nisus" would regulate the give corresponding size to the vessels & nerves &c, supplying much fact, without the direct aid of selection though this might always come into play. I, also just

I alluded in the first chapter to the mechanical action, attributed by Vrolik, to the shape of the bones of the pelvis of the mother on the head in the dif of the individual human embryo in different races. a [text excised]

[34v]

[For readability, this paragraph which Darwin scored is not crossed]

 *C.C. Sprengel in his "Das Entdeckte Geheimnis Tab XX gives figures of two kinds of achenia f in [illeg] & Picris & Tussilago so that the difference does not seem to stand in relation to whether or not the exterior florets have a [text excised] corolla.—

(34 bis

(a) text

so in the species of Birds, in which In various groups of Birds, the form of the kidneys differs remarkably, & M. St. Ange (Annales des Science. Nat. 1 Ser. Tom 19 p. 327) attributes these differences to the varied shape of the pelvis, which may be said would seem to have acted mechanically on them; as the & the form of the pelvis which would probably stands in direct relation to the [illeg] be

different powers of locomotion. So again in Snakes, Schlegel **Essay on Serpents, Engl. Translat. p. 26) has remarked that the varied positions of the heart & of the lungs, the riband-like liver with the gall-bladder removed from it, the anomalous position of the kidneys & organs of generation, all stand in direct relation to the shape of the body, formed for crawling, & to the manner of swallowing: how much of these remarkable modifications ought to be attributed to selection & d direct selection acting on slight variations in these important organs, & how much to the indirect, & almost mechanical action of changes in the form of the body & of jaws of the mouth, it would be very difficult to say.)

In our first chapter I showed that M Isidore Geoffroy St. Hilaires law of the multiple parts whether physiologically important or unimportant varying much, in number, holds good both in regard to varieties

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(Ch. 7. Correlation of growth)

& to species; I presume that this may be accounted for by a more or less of the stands in relation to a greater or less amount of plastic matter, out of which the multiple organs have to be developed, having been formed accumulated at an early embryonic age.)

(Homologous Homotype parts it may be so tend to vary in a so similar manner, owing, it may be supposed, to their similarity at an early embryonic period; or one homologous part tends in its variation to imitate another pa part of an homologous the same homotype nature. Thus the great anatomist Meckel, to quote th a has insisted, as stated by Isidore Geoffroy Saint-Hilaire (Hist. Gen. des Anomalies Tom. I p. 635) "que les muscles du bras, de l'avant-bras et de la main ne s'ecartent presque jamais de leur type normal par le nombre, et la disposition de leurs parties, sans tomber dans les conditions qu'offrent dans l'etat regulier, les muscles de la cuisse, de la jambe & du pied; et reciproquement."

(Homologous parts both in animals & plants seem to have a strong abnormal tendency to cohere or unite; *& the variations thus caused, can often be so closely paralleled by normal structures, that it is difficult to believe that the parallel is accidental.)

[35v]

[For readability, this paragraph which Darwin scored is not crossed]

Correlation of growth: In I Ch. Under the head of I my [illeg] [illeg] as being a species I touched on several laws governing varieties the existence of which not only fully be disputed which ca be most obscurely understood, I remarked on I. St Hilaire law of multiple organs varying but under domestication, & I attribute it to domes for organism in a state of nature, so that I approached [text excised] the production of the species

[35vv]

 *Isi. Geoffroy. Hist. Gen. des Anomalies. Tom I. p. 541, 545.— For plants see M. Moquin-Tandon Elements de Tératologie Vegetale. 1841. p. 248, 267.

(35a

Insert in p. 35

(Ch. 7 Correlation)

(Moreover it would appear that multiple parts are more especially apt to be variable in form as well as in number. M. Isidore Geoffroy (Hist. des Anomalies Tom I. p. 60, 638 650. Tom. 3. p. 456) insists on this; remark & M. Moquin-Tandon (Teratologie Végétale p. 124) observes that "les organes répetés le plus de fois sont aussi ceux dont le developpement est le plus variable." As this "vegetative repetition", to use Prof. Owen's expression, is a sign of a low or little specialised organisation, the foregoing remarks on the variability of multiple parts seems to fall under an remark observation often made by naturalists that the lower animals are more variable than the higher. And with plants, Dr. Hooker insists remarks (Flora Indica Introduct. p. 29. & Ranunculaceae p. 2.) that "variations in the floral organs are apparently more likely to occur the less the individual parts deviate from the normal type, the leaf; as if the th more complete adaptation to a special function rendered them less liable to casual variation." One case Or as the

(see Back page)

(35B

(Ch. 7 Correlation)

case may be put, as long as an organ had to act in many ways, its exact form would probably not signify; just as a knife for cutting all sorts of things, may be almost of any shape, but a cutting tool for some particular object must had best be of some particular shape; but and as soon as the organs had began to act be similarly thus specialized, natural selection would be constantly seizing so with an organ as soon as it began to be specialised through natural selection for some particular end, its particular structure would become more & more important; & this same natural selection would tend to keep the form constant by the rejection of accidental deviations, excepting indeed such few as tended to improve the organ; & these it would seize on; whereas until the exact shape or structure of the organ became important for its function natural selection would hardly come into play in checking slight any slight deviations fluctuations in its form.

(35C (36

(Ch. 7 Correlation)

There can be no doubt, that many parts of the organisation of every living thing are correlated together, so that if one part changes, another part will tend to change, by bonds by a bond which we can sometimes dimly see dimly but & often cannot not at all. Some instances were given in the first chapter of variations thus related; for instance hair & teeth believed by most physiologists to be of an homologous nature in the so-called Turkish or naked dogs: now if we take a general survey of the mammiferous Kingdom, the two classes orders which are most anomalous in their teeth, namely the Edentata & Cetacea, are certainly most anomalous in their dermal covering; as we see in whales, contrasted with seals, & in the armour of the armadillo Mylodon &c & Ant-eater.

I presume the remarkable fact of the seedling Cuscuta like ordinary not having cotyledons, though germinating in the soil, stands in direct correlation with the mature plant being parasitic on the elaborated sap of other plants & so not requiring leaves.

(As I have said the bond of correlation is often quite hidden from us; remember the blueness of the eyes & deafness in cats,—the nakedness of young pigeons & their colour—

[36 bis]  

by my [text excised]

this low is common to species, variation & [text excised]

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constitutional differences & complexion &c. So in the gravest & trifling in unimportant monstrosities Is. Geoffroy (Hist. des Anomalies &c Tom 3. p. 402) remarks "que certaines anomalies coexistent rarement entre elles, d'autres fréquemment, d'autres enfin presque constamment, malgré la difference tres grande de leur nature, et quoiqu'elles puissent paraitre completement independantes les unes des autres". In looking at normal organic beings in their normal state one incessantly meets sees in all the species throughout whole groups of animals & plants, having very wholly quite different habits, two parts of their organization similarly having no apparent connection, alike yet [slip of paper pasted over] strongly tempted to put

almost identical throughout all the species: but it is most difficult in such cases to know whether there is any correlation in the parts. The mere fact of the community of structure in the two parts throughout many allied forms is no proof whatever, according to our theory, of any correlation of growth, for the community it may be wholly due to community of descent. And in the ancient parent of the allied forms, the two parts may have acquired their present structure & apparent connexion, from having been independently modified for separate purposes through natural selection. Just as the Fancier is now making by artificial selection the beak of his tumbler-pigeons very short, & the feet very small, without, perhaps, there being any correlation whatever in the growth of these parts.*a

[37v]

*a But it would be rash even in this case positively to assert that there was no correlation; for it is well known that acephalous monsters are especially liable to have imperfect feet.-

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(Ch. 7 Correlation of growth)

On the other hand, when in a group of species, the same part or organ differs in each, such differences are very generally, perhaps universally, accompanied by at least slight differences in the surrounding parts. Thus Prof. Owen (a) text

[For readability Darwin's horizontal and vertical crossed lines are left undeleted]

utterly disbelieves that the jaw in any one instance is exactly the same in two genera of mammals having differently constructed teeth. Such differences in the connected parts, jaws has when slight & apparently unimportant in function, may in all probability be attributed to correlation of growth.

As we can hardly suppose that internal & structural differences in the seeds fruit of on the same individual plant can be of use to the species, we must attribute the differences in the seeds pericarps,—in their shape, their peppersappendages, & even in the ovary itself with its accessory parts *a — of the central & marginal florets of many compositæ, to some correlation of growth. Possibly it may be a case of compensation, yet there does not seem to be any direct

[38a  

The umbelliferæ with lax heads oftenest have ray florets. Box seed differs in some cases in

In carrot, (Harvey) is central floret flowers with which is enlarged & sterile. This looks against pressure. Is it conceivable that pressure in Hasselquistia & Coriander could make seeds orthospermous & cœlospermous.

In Marygold seeds are convex externally looking like pressure.

Seeds differ in ray & centre of some Compos, without differences of corolla.

Would seed ovary or corolla be first formed? as first formed most likely to affect last formed.—

Heads of flower rendered more conspicuous in Viburnum & in Mussænda (by the exterior ray of sepal being white; their flower not sterile) by the exterior flowers being developed. In Feather Hyacinth by central.—In carrot central flower also affected, as in peloria.—

These facts seem to show that some connection with more or less nourishment of central or exterior parts.

[38av]

The phenomenon not more frequent in densest heads.

[38v1]

a text)

remarks (Proc. Geolog. Soc. 1842. p. 692) that "he knows of no analogy in the whole mammalian series that would justify a belief" that the lower jaws should not be quite similar different in two genera, characterized by a difference in the number of their teeth.

[38v2]

*(a) An H. Cassini in Annal. des Sciences Nat. 1 series. Tom. 17. p. 387.— C. C. Sprengel in his Das Entdeckte gives figures Tab xx of the achenium in central & ray florets of Picris (Helminthia) & Tussilago; Thrincia offers another instance.

(38b

(Ch. 7 Correlation of growth)

relation between the state of the seed fruit & the presence or absence of the ray-like corolla in the outer florets. Possibly the differences may be related to the mutual pressure of the florets flowers: at least the Decandolles*(a) *(a) (Mém. Soc Phys. de Genève. Tom. 9 p 78) are inclined, in the case of certain states of Dianthus polymorphus, to account for the abortion of the anthers & the greater or lesser or lesser length of the style "to the lateral compression of the flowers in the cymes." But it seems extremely doubtful whether this explanation (P) is applicable can be applied can be applicable to the differences in the internal structure of the seed, which has been observed in in believe the exterior & interior inner & outer flowers in some Umbelliferæ: thus in Hasselquistia*B the seeds of the ray-flowers are orthospermous & those of the disc coelospermous; & analogous differences have been observed in the Coriander; their difference it is, I may add, to show how important these differences of this kind are that Decandolle has founded on them the classification of the Family order. (P)

Certain Leguminosæ plants bear on the same sp plant flowers of two different kinds, & with the

[38bv]

(P) is applicable: in the carrot the central flower has the corolla developed It is by no means the Umbelliferæ with the densest heads, which have the corolla most fre frequently developed in the external flowers; & in the carrot it is the central flower which is developed in an unusual manner. Perhaps, this whole class of facts are in some way related to the same nutrient flowing more freely to the central or exterior florets, & may be connected with causes which tend to produce peloria in the line of the axis. But in some instances I suspect, that C. C. Sprengels view that the exterior florets are developed & one bit of calyx in Mussænda to make flower conspicuous to insects.

[38bvv]

*(b) Tausch in Annal. des Sciences Nat. 2 series Bot. Tom IV. p. 41. State what difference

(38c

(Ch. 7 Correlation of growth)

flowers, as I am informed by Mr. Bentham, the pod sometimes differs. Ad. de Jussieu has described*(a) (*(a) Archives du Mus. d'Hist. Nat. Tom. 3. p 82) th two different kinds of flowers borne by certain species of Malpighiaceæ; one flower of the ordinary kind sort, the other without a corolla or with a mere rudiment of it, two ovaries without a style &c; so that Jussieu remarks in these degraded flowers "the greater number of the characters proper to the species, to the genus, to the family, to the class disappears, which thus laugh at our classifications". Nothing is known of the use or meaning of the two kinds of flowers borne by these & other plants, but I presume that the internal & structural differences in the imperfect flowers & seeds, which, however, seed as well & often better than the perfect flowers, must can be of no service to the plant, & must be are due to some correlation of growth.

To give an instance of a correlation, which I should attribute

[faint pencil note:] Nectary & petiole of column in Pelargonium

(To give one instance of a correlation, which I should attribute wholly to natural selection, & not to the laws of growth; it has been winged seeds are here found*c

[38cv]

*(c) Alph. De Candolle in Annales des Science Nat. 2 series. Bot. Tom XI. p. 281.

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(Ch. 7 Correlation)

in an indehiscent fruit; or, as I should put the case, seeds could not become winged through natural selection only in fruit which opened, so that the seeds which were blown furthest got an advantage over those less fitted to be acted on by the wind, & thus gradually became winged; & this could never happen through natural selection in a fruit which did not open.)

(Those who have studied monstrosities believe,*(a) that any affection of a a part at first developed during the early life of an the embryo tends to modify so many other parts of the organization subsequently developed. This seems so natural that it can hardly be doubted; & hence the later formed structures parts of the organized structures of an animal as they are necessarily subjected to the influence of all previous abnormal changes, likewise are more the most liable to monstrosities & variations. than the earlier formed structures On the same principle Moquin T monstrosities of axis of the plants almost always affect the appended organs structures.*(a)

We may infer from these considerations that the same cause tending to produce a monstrosity or variation would produce different results according to the period at which it acted on the embryo. Perhaps we can may understand to a certain extent understand those sudden & great variations,

[39v]

 *Isidore Geoffroy St. Hilaire Histoire des Anomalies. Tom I p 484. Tom 3. p. 392 Andral was strongly of the same opinion.—

*(B) Moquin-Tandon Elements de Teratologie Vegetale. p. 113.

(40

(Ch. 7 Correlation)

called by horticulturists 'sports', whether in the bud or seed, by supposing that a modification takes place at a very early age of development & greatly disturbs the whole organisation. I think there can be no doubt that in those animals, which live an independent & active life in their larval condition, any great modification at this period would sensibly alter the structure of the mature animal; & as many insects, when mature, life live for a very short time, & do not never even feeding, have nothing to do but procreate their time kind, the greater part of much of the difference between species & species, may well in many cases be almost wholly due to correlations with their larval condition: on the other hand modifications in the mature state will generally almost necessarily have been preceded by modification at an earlier age. It must not, however, be supposed that a great amount of change, caused by the continued addition through natural selection of small changes, of any one organ, or at any one period, necessarily causes a correspondingly great change in all other parts of the organisation; or at all other periods of life; for I think the facts given in the first chapter on the affected results on the changes due to selection under domestication, show that such is not the case.

[41a1]

[Letter from T.H. Huxley not transcribed]

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[Letter from T.H. Huxley not transcribed]

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[Letter from T.H. Huxley not transcribed]

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[Envelope]

[41a2]

There is only one point in which I cannot follow you. — Supposing Barneouds I do not say Brullés [2 words illeg]remark were true & universal, i e & that one pet the petal which has to undergo the greatest amt of development or modification begins to change the soonest from the simple & common embryonic form of all the petals; then I cannot but think it wd throw light on Milne Edwards proposition that the more different wider apart the classes of animals, the sooner do they diverge from the common embryonic plan.—which common embryonic plan type plan, may be compared to the similar petals in the early bud.—the several petals in one flower being compared to the distinct, but similar embryos of the different classes.—

I see in my abstract that M. Edwards speaks of the most perfect & important organs being first developed & I shd have thought that the [3 words illeg] not developed.

[41a2v]

1857 Huxley on Brullé Barneoud

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Do not copy this Heading or pages

M. Brullé in a memoir on the embryonic transformations of the Articulata (Annales des Sci. Nat. 3 Series Zoolog. Tom. 2. p 273) insists "qu'un appendice se montre d'autant plus tot, qu'il doit acquerir un development plus complet". In another part he strongly reurges the truth of this proposition, & asserts that the reverse converse holds good. It would almost appear according to this view as if more time were required for the growth of a part which has to undergo greater embryonic modifications, & that consequently its development had to commence earlier. M. Barneoud (Annal. des Scien. Nat. 3 series Bot. Tom. 6. p. 270, p. 287) has shown that something analogous in plants having irregular corollas flowers; for he finds in an Aconite, in cert Orchidaceæ, Labiatae & Scrophulariaceæ, that at a very early age the petals are equal & similar; "mais bientôt on remarque entre dies, une difference de grandeur d'autant plus forte et plus précoce

(42

que la fleur est plus irreguliere a l'etat adulte".

So that in these cases, the parts which have to undergo most modification from their archetype, grow quicker than the less modified parts.

Prof Milne Edwards (Annales des Sci. nat. 3 Series Zoolog. Tom. 3. p 176) makes a different but somewhat analogous comparison: he does not compare parts in the same individual developed from similar & homologous elements, but the same functional system in quite different groups of animals; & he seems to think that according as the organs in question are most developed in any class, the earlier they appear in the embryo in that class: thus he adduces as one instance contrasts the circulatory system in the Vertebrata, in which it is so highly perfected, with the same in Annelids. Indeed the grand & fundamental principle main groundwork basis of all affinities, so strongly insisted on by Milne Edwards in this paper & elsewhere, (Annal des Science. Nat. 3 Series Zoolog. Tom. I p. 65.) seems to hang on the same principle,—namely that the more widely

(43

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two animals differ from each other, the earlier does their embryonic resemblance cease; thus a fish on the one hand, & mammals together with birds on the other hand branch off from the common embryonic form earlier then does do the at a very early period, whereas mammals & birds being more closely related to each other than to fish, from branch diverge from each other at a later period. This seems to accord with M. Brullé's principle that the more each part is changed from the common archetype the earlier it is developed; for as a fish differs in nearly all its organization from a mammal, more than a bird differs from the mammal, the fish as a whole would have to be differentiated at an earlier period than a bird. So with Mr. Barneoud's case, if we look at an irregular flower at a period between its earliest condition & maturity, the more irregular & modified petals from having grown at a quicker rate may be said to have been earlier developed. I presume that actual time is not referred to in any of these cases; only relative time one organ being compared with another; for, as is well known, the heart of the chick arrives at the same stage

(44

(Ch. 7 Correlation of growth)

of development with that of a mammal in a far shorter actual period of time.*)

If the foregoing principle be really true & of wide application, it is of importance for us; for then we might conclude that when any part or organ is greatly altered through natural selection it will tend either actually first to appear to be formed at an earlier embryonic age than other agency or well to grow at a quicker rate relatively to the other organs than the other parts & organs it did before relatively to the other organs: it had undergone modification: consequently, as we have seen in the case of monstrosities this early formation will tend to act on the other & subsequently developed parts of the system. This same principle will would, also, probably play an important part in the following so-called law of balancement or compensation of growth.

[44a]

[in the hand of Ebenezer Norman]

(1

11

M. Brullé in a memoir on the embryonic transformations of the Articulata (Annales des Sci. Nat. 3rd Series Zoolog. Tom. 2 page 273 282-285) insists "qu'un appendice se montre d'autant plus tot, qu'il doit acquerir un development plus complet". In another part he strongly reurges the truth of this proposition, & asserts that the converse holds good. It would almost appear according to this view as if more time were required for the growth of a part which has to undergo greater embryonic modifications, & that consequently its development had to commence earlier. M. Barneoud (Annales des Science Nat. 3rd Series Zoolog. Tom. 6 pp 270, 287) has shown something analogous in plants having irregular flowers; for he finds in an Aconite, in Orchidaceæ, Labiatæ & Scrophulariaceæ, that at a very early age the petals are equal & similar; "mais bientôt on remarque entre dies, une difference de grandeur d'autant plus forte et plus précoce

[in margin, faint pencil note:] I ought to look [illeg] Ch paper

Prof Milne Edwards (Annales des Science. Nat. 3rd Series Zoolog. Tom. 3. p 176) makes a different but somewhat analogous comparison: he does not compare parts in the same individual developed from similar & homologous elements, but the same functional system in quite different groups of animals; & he seems to think that according as the

(40 to 45

(Ch. 7 Balancement)

Law of Compensation or Balancement: Geoffroy St. Hilaire & Goethe advanced the law brought forward about the same period this law, which has been admitted by some naturalists & great utterly rejected by others: it seems to me that there are gr the gravest difficulties in proving its truth, of this Law & yet I must think that that there is some truth in it. it holds good to a large extent. Goethe puts the case under a clear point of view, when he says (Pictet on the writings of Goethe, translation in Annals & Mag. of Nat Hist. vol. 2 p 318 1839) that "the budget of Nature is fixed; but that she is free to dispose of particular sums by any appropriation that may please her. In order to spend on one side, she is forced to economise on the other side." That this sort of compensation holds good with the modifications which our domestic productions have suffered, I can hardly doubt after the facts given in our first chapter; for instance the [illeg] that the sterility caused in plants rendered sterile & seedless by their artificial treatment of many plants in one garden allows the nutriment which ought to have gone to the seeds, the nutriment goes to the enlargement of the fruit.

[45a]

[in the hand of Ebenezer Norman]

(2

organs in question are most developed in any class, the earlier they appear in the embryo in that class: thus he contrasts the circulatory system in the Vertebrata, in which it is so highly perfected, with the same in Annelids. Indeed the main basis of all affinities, so strongly insisted on by Milne Edwards in this paper & elsewhere, (Annal. des Science. Nat. 3rd Series Zoolog. Tom. I p. 65) seems to hang on the same principle,—namely that the more widely two animals differ from each other, the earlier does their embryonic resemblance cease; thus a fish on the one hand, & mammals together with birds on the other hand branch off from the common embryonic form at a very early period, whereas mammals & birds being more closely related to each other than to fish, diverge from each other at a later period. This seems to accord with M. Brullé's principle that the more each part is changed from the common archetype the earlier it is developed; for as a fish differs in nearly all its organization from a mammal, more than a bird differs from the mammal, the fish as a whole would have to be differentiated at an earlier period than a bird. So with Mr. Barneoud's case, if we look at an irregular flower at a period between its earliest condition & maturity, the more irregular & modified petals from having grown at a quicker rate may be said to have been earlier developed. I presume that

[45b]

[in the hand of Ebenezer Norman]

(3

actual time is not referred to in any of these cases; only relative time one organ being compared with another; for, as is well known, the heart of the chick arrives at the same stage of development with that of a mammal in a far shorter actual period of time.

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(Ch. 7 Balancement)

going with & enlarging the fruit. or petal instead of

In an monstrosities this law seems, also, to hold good: Isidore Geoffroy St. Hilaire gives the following example as the best out of hundreds, "dans lequel l'antagonisme de développement m'a semblé" aussi evident que possible. II existait en effet du côté" gauche un rein & une capsule surrenale de grandeur ordinaire, et du côté1 droit, un rein extremement petit et une capsule tres-volumineuse." (This case (Hist. des Anomalies Tom I. p. 276. This case is quoted from M. Martin St. Ange.) M. Moquin-Tandon gives several cases of this same law in monstrosities in the vegetable Kingdom. (Elements de Teratologie Vegetale. p. 155-160.) Henslow's case of pistil

But the question which here more immediately concerns us, is whether we can discern the effect of this law in the structure of species in their normal condition. The case of separate has been advanced as one of the numerous ribs & abortive extremities in separate the ribs being so numerous & the limbs absent in serpents has been advanced as one of 1compensation of growth; & it may be so,

(47

(Ch. 7 Balancement)

but as, [illeg]according to the principles of this work, a part may be decreased diminished by disuse, & another neighbouring part augmented by use or still more effectually by continued natural selection (for instance the greatly enlarged lengthened palpi & antennæ in the eyeless cave animals), I do not see how such results are to be distinguished from true compensation of growth. Nevertheless so many cases of apparent compensation of growth can be advanced, that I conclude there must be some truth in the law. For, as Mr Waterhouse has remarked informs to me that he is decidedly of opinion has remarked to me, it would appear that when any part is greatly increased, adjoining parts or organs do not retain their their size usual or typical size, but are lessened actually diminished.

The large size of the canine teeth & the smallness of the premolars in the Carnivora may be given as an instance. The great size of the thorax & the smallness small size of the abdomen in the Brachyurous Crustaceans & the largeness of reversed case exactly converse case in the Macroura, have been advanced as cases of compensation: From Adouin, for whose opinion

[47v]

(Ch. 7 Balancement)

but I can hardly do not see how we are to eliminate distinguish the effects of disuse of our organ & greater use of another neighbouring part, from single compensation of growth;

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one must entertain the highest respect, insists most strongly (Annales des Sciences Nat. Tom I (1' series) p. 111. & 416) on the [illeg] mutual relation in size development of the three divisions of the thorax, in the several great orders of insects.

(The following great Botanists seem to believe in the law of compensation, not merely in monstrosities, but in normal forms, if in plants in their normal state; De Candolle, the elder, Richard Moquin-Tandon & Auguste de Saint-Hilaire. This latter Botanist, (no relation of the founder of the law theory)) in his excell gives as instances of compensation, the relations of limbs expansion of the petiole, with [illeg] aborted & the abortion of the limb in many leaves;—the great development of the bracteæ into a tuft when the towards the summit of when when flowers are not developed as in the crown of the pineapple;—& a crowd of instances in which the doubling of the organs in one whorl seems to cause the abortion of the part organs in the succeeding whorls. (Lecons de Botanique 1841. p. 145, 199, 619.) Again in Annal. des Sciences Nat. Bot. 2 series Tom I. p. 333. he advances this law in relation to stamens & petals in certain genera.)

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(Ch. 7 Balancement)

Moquin-Tandon, besides cases quoted from Decandolle & some monstrosities (Elements de Teratologie p 157) brings forward as a case of balancement, the elongated peduncles & bright-colours of the rudimentary flowers in the Feather Hyacinth; & again the development of the corolla & the abortion of the stamens & pistils in the outer flowers of the Snow-ball-tree (Viburnum opulus); & something of the same kind would appear to be common hold good in the outer florets of many Compositæ & some Umbelliferæ. Ach. Richard (Annal. des Sci. Nat. Tom 2. 1 series, p. 15) believes that the great size of the bulbillas in certain Crinums causes the pericarp in these species to be almost rudimentary.

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If one could feel thoroughily convinced of the truth of this law of compensation, it would be important. On our view of species having arisen like varieties we could understand its action. (& we need not call in fresh creations to play the part of the laws of simple growth.) The order of the development of parts would probably become be seen to be a very important element in change; if the law of compensation be as powerful a law as many have thought, for the first developed parts would be apt to rob & so cause the deterioration of subsequently formed parts. It would, also, I believe, throw some light on rudimentary organs & parts. But

I have sometimes been inclined to think that the supposed law of compensation might be put under a simpler form; namely that nature, like a careful manufacturer, always tries to be economical in her materials; & if any part or organ can be spared, whether or not any adjoining part be in consequence largely developed, it is set is spared, & matter so

(51

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saved. Animals of many orders belonging to very different group classes, when parasitic within other animals & thus protected, offer many many instances of this truth: I am thinking of th two Cirripeds namely Proteolepas & the male of Ibla which also live within other animals, many within other the sacks of other cirripedes, & in both of these & in no other member of the class the entire capitulum or carapace is absent & thus saved. In many such [illeg]cases, I doubt whether it can be truly always said that any other part or organ has been, either as cause or effect, developed in excess; but the less saving of nutriment required, owing to some useless parts of the body becoming useless having been rendered under changed circumstances & not sa being developed through natural selection less & less developed, might be of service to any creature in the severe struggle for life to which all are exposed: just as on the same ground more individuals could be kept alive pasture a greater number of animals in a moderately thin thin state, than of could be kept alive, than of animals excessively fat with a thick layer of fat.) all over this

[52a]

remark to nearly this effect; Professor Owen, also, seems to have come independently to a similar conclusion. I was formerly much struck with Mr. Waterhouse's remark, for I could see no reason why in a species, if looked at as an independent creation, a part developed in any highly peculiar manner or great degree to an extraordinary size should tend to be eminently variable: on the other hand if a species be only a strongly marked variety, the cause of this variability, we shall see, is not of very difficult explanation.

(52

(Ch. 7. Abnormal development variable.)

A part normally normallydeveloped in any species in an extraordinary degree or manner, in comparison with the same part in this allied species, tends to be highly variable.—

Several years ago, I was struck by a remark remark generalisation to nearly this same effect published by Mr Waterhouse Mr. Waterhouse *published a of our present heading, (not confined to maximum of development which includes any striking peculiarity of structure as well as more great maximum of development.

Professor Owen, also, independently seems to have come to a similar conclusion. I was formerly much struck with this Mr. Waterhouse's remark, for I could see no reason why in a species, if looked at as an independent creation, [remainder not transcribed]

[52v]

 *A. Nat. Hist. of the Mammalia. 1848. vol. 2. p. 452, note, "As a general rule where any species is characterized by a maximum of development of certain parts, those parts are more subject to variation in the different individuals of the species than are parts which approach more nearly to the normal conditions."

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(Ch. 7. Abnormal development variable.)

(I must here premise that the our apparent law, which we are here discussing going to discuss relates only to parts differing greatly from the same parts in species if not actually congenerous or at least rather pretty rath closely show allied species oftentimes at least pretty closely allied: nor do I suppose that the rule is of universal application. To give an imaginary example, the wing of a Bat is a part developed in a highly remarkable manner in comparison with the front-legs of other mammals, but our law would not here apply: it would apply only to some one one Bat having wings developed th in an extraordinary size degree, or in some extraordinary manner, compared with other closely allied Bats, more especially if compared with other Bats of ranked by natural selection in the same genus. If When several species within the same genus differed remarkably one from the other in some part or organ, which generally presented constant character is a uniform throughout the rest of the same Family, to which the genus belongs, then according to our law, the part or organ in question would should tend to be variable in each the species of the genus. Our supposed law is applicable to any character, although attached exclusively to either male or female sex, if the character be very remarkable in comparison with the same part in the corresponding sex of the

(54

(Ch. 7. Abnormal development variable.)

allied species. Moreover as all secondary sexual characters, wheth whether or not developed in any especial manner, may be considered as in some degree a departure from the typical structure of the group to which the species in question belongs,*— for instance the male Turkey, Fowl & Pheasant all depart a little more from the normal typical structure of the Gallinaceæ than do the females; so does the female common glow-worm depart far more from the typical structure of the Lampyridæ than does the male,—hence it seems to be conformable to the same our law, that all all secondary sexual characters should be far more variable, as I cannot doubt believe in the cases they are, than the characters common to the two sexes.

Before giving a list of the more striking facts, on which I have accidently met with, I must remark in some regard to the its shortness of the list that in the first place the cases implying extraordinary development cannot be very frequent; & secondly that it is very difficult to collect much facts of this kind: w I have experienced it this myself, & have seen it in others, namely that it is scarcely

[54v]  

 *W. Hunter's Animal Oecomnomy pe Edited by R. Owen p. 47. ­— Westwood in Entomolog Discourse has made previously same remark.

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(Ch. 7— Abnormal development variable)

possible, on being asked, to call to mind relations of a complicated kind without going deliberately through every species in a group with which one must be thoroughily familiar. Having been struck with Mr. Waterhouse remark before I undertook the classification of the Cirripedia I attended to this point it & was struck with astonishment astonished at it's a wide application; so that I several times generally found a some most striking & remarkable character in a species of comparatively little far less use for classification than I had anticipated owing to its surprising variability.*(Monograph of the Balanidæ. Ray Soc. 1854. p. 155)

Moreover from Cirripedes are being hermaphrodite, the cases are the more valuable, as clearly showing that the law holds good without any relation to sexual distinctions.

As Birds are generally remarkably constant in their character structure, I have also particularly attended to those few cases in which, in comparison to closely allied birds, some part presents a very unusual character, & we shall immediately see how apt these characters are to be universally variable. These fact cases of Birds, together with my own experience with cirripedes, have

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mainly convinced me that there is much truth in our supposed law.—

(a) text

Naturalists have repeatedly remarked that every part of the living frame can be shown to be variable in some group species or another species: hence, as a mere coincidence, I should have expected that some few instances would have occurred of parts developed in any high remarkable manner degree, being likewise variable in the same species. But it must be remembered that instances of organs parts developed in great excess or very differently from the same part in allied species are not numerous; & secondly that the cases of variability in organs which are usually constant in form (of which fact we have several instances in the following list) are decidedly rare; therefore the improbability is very great of the variability, itself rare, being a mere chance concomitant, of unusual development, also rare in the same part or organ in the same species. But as we shall see that such cases coincides do occur not rarely, we must Hence, I think, we may Therefore we may infer that there is some direct relation between the variability

[56v]

(a) text p. 56)

On the other hand I have been led to doubt its truth of the [proposition]from not having noticed any analogous remarks in Botanical works, & I believe in the present state of Natural History Botanical generalisations are more to be trusted than those deduced from Zoology Zoological. I applied to Dr. Hooker on this subject, who after careful consideration, informs me that though some facts seem to countenance the idea rule, yet quite as many or more are opposed to it. In plants one large class of cases, namely secondary sexual characters are not present. Moreover, as Dr. Hooker in strongly remarks has remarked to me, in all plants there is so much variability, that it becomes very difficult to judge of a greater or lesser form a judgment on the degrees of variability: in a Bird having an a beak of unusual structure we are at once struck if it varies, for the at any variation, as the beak in other birds the beak very seldom varies; but with a plant, how difficult to judge whether an abnormal leaf or petal varies more than leaves or petals of ordinary forms! Here

In parts developed to a great size, a source of deception should be

here noticed; namely that the variation, even if not really greater than in other species in which the same organ is of less the usual size, would be far more conspicuous. But this source of doubt does not apply to parts developed not to a great size, but in an unusual manner.

(57

(Ch. 7— Abnormal development variable)

& the unusual, though normal, (although normal & not monstrous), development of the same part. I may here add that many naturalists believe that variability is a related to the slight functional importance of the part: I do not myself believe in this doctrine; but it is therefore worth notice that when a part or organ is developed in a remarkable manner in a particular species, the most obvious inference is that it is of at least as much, probably of more, importance to the species in question, than the same part or organ where less developed in the allied species; & yet, as we shall immediately see, it is nevertheless often generally highly variable.

(58

(Ch. 7. Cases of abnormal & variable parts)

The Hystrix cristata has a skull readily distinguished by "the enormous size of the nasal bones," but these bones, & "the highly arched upper surface of the cranium "are subject to considerable variation". (Waterhouse. Nat. Hist. of Mammalia vol. 2. p. 452.

[pencil note:] Zoolog. Soc. beginning of 1857

Owen Length of arm of ourang-outang longest arm & very variable in length—Owen has some other cases about teeth I feel sure Falconer tusks of Elephants but the sexual Elements certainly variable but not confined to a species or genus

[pencil note:] To give a few instances of male sexual characters variable—Tusks of Elephants Narwhal Mane of Lion if Persian be same species—Deer Horns v. Bull

The male Narwhal has, perhaps, the most anomalous teeth of any mammal, & here we have variability in the length, of the tusk & sometimes two — instead of one of the incisors are developed into the well-known, remarkable tusks: both incisors the second incisor is developed into a short tusk.

Scoresby. Arctic Regions vol. I. p. 490.—Kane's Arctic Exploration vol 1 p. 455.

[pencil note:] I have looked in Penny Encyclop. & Dict. Class & can find out no other particular of variability.

(58v

Gleanings from the Menagerie of Knowsley Hall 1850. J. E. Gray p. 55. Though Horns in Deer (a sexual character) are of service for higher division of the separating the species into groups. & though they have largely been used for specific distinction, yet Dr. G. finds, yet it has been f. that animals of same herd or even family & sometimes even the same specimen under different circumstances, under different in succeeding years have produced Horns so unlike in size & form, that they might have been considered as belonging to different species

See good case in Sir J. Richardson Fauna, p 241

5 12

(59

(Ch. 7. Cases of abnormal & variable parts)

The Wax-wing, Bombycilla garrula, is very remarkable from the secondary wing-feathers being tipped by scarlet horny points which differ a little in the male & female: Macgillivray says adds "the principal variations have reference to the wax-like appendages to the secondary quills": British Birds vol. 3 p. 535.

The Chimney Swallow, Hirundo rustica, which differs from many of its congeners, by its forked tail, which is much shorter in the female: Macgillivray says that males it exhibits little variation, except in the tinge of the red on its breast "& in the lateral tail-feathers being more more or less elongated." British Birds vol. 3. p. 560

The Oyster-Catcher, Hæmantopus ostralegus, certainly has a remarkable beak, & Macgillivray says "considerable differences occur in the size of the bird, & especially in the length & shape of the bill." British Birds vol. 4. p. 155

The Cross-Bill, Loxia Europæa, has a most singular bill, as its name implies: several ornithologists have been struck by its great variability: Macgillivray says "the variations which I have observed in adult birds are not remarkable, excepting in regard to size, & especially in that of the Bill, which varies considerably

(60

(Ch. 7. Cases of abnormal & variable development)

in length, curvature & the degree of elongation of lower mandible." He then gives various measurements showing how remarkably great the variations are in this important & generally constant part of the Bird's structure: British Birds. Vol. I. p. 423.— (a) text see, also, Yarrell's British Birds, &c

Blyth in

[faint pencil note:] Puffin see Yarrell [2 words illeg] Graba or Macgillivray or Penny Encyclop

The long-legged Plover or Himantopus is an extraordinary bird, compared with its allies forms a small genus with closely allied species, differing widely quite remarkable from their extraordinary length of the legs compared with their nearest allies. Mr. Gosse (Birds of Jamaica p 388) has carefully measured attended to the measurements of the legs in H. nigricollis, & he finds no two birds with exactly the same length of leg, there being as much as half an inch in length difference between the extreme specimens. This bird is likewise remarkable by its bill being slightly upturned; but Mr. Gosse finds this character well pronounced in only one out of 16 or 18 specimens.— Mr Hills has

[60v]

(a) text

The upper mandible, moreover, sometimes crosses from the right & sometimes from the left; & this variation is the more remarkable, as certain muscles are unequally developed on the two sides, in accordance to the side to which the upper mandible crosses over: Yarrell in Zoological Journal. vol. 4. p. 459

(59 bis (60a (60 bis)

(Ch. 7. Cases of abnormal development. var.)

In Trochilus polytmus the curvature of the beak seems in some degree a sexual character, being according to Mr. Gosse (Birds of Jamaica p. 98) plainest in the female; but the curvature "varies in the individuals", & I possess several females whose beaks are more curved than in T. mango."

(One of the species of Chamelion (C. bifurcus) is most curious extraordinary from its front of its head its nose being divided & produced into two sort of horn-like protuberances; but H. Schlegel (Essay on Serpents Engl. Translat. 1843. p. 216) says that "the nasal prominences are subject to variation."

In the species of the genus Cygnus, the trachea in some species follows the usual course, in others it makes the most remarkable convolutions, entering the breast-bone, & these convolutions differ greatly in some of the species; in the Whooping Swan "the diameter of the trachea & the extent to which it enters the crest of the sternum varies"; in Bewicks Swan, also, the trachea is not constant, the horizontal loop being sometimes absent, & in some specimens it does not differ from that of the Whooper. (E. Blyth in Calcutta Review 1857. p. 155. and Macgillivray British Birds vol. 4. p 651, 665.)

(61

(Ch. 7. Cases of abnormal & variable development)

Cirripedia

cirripedes.— In Conchoderma the valves are very abnormal in shape & remarkably astonishingly variable but then they are in some degree rudimentary in the species. One species of Conchoderma differs from all cirriped other Lepididæ Cirripedes in having curious ear-like appendages to the capitulum & these, also, are very variable. Alepas cornuta differs from the other species of the genus in having horn-like projections on the capitulum, & these are very variable in shape & position. Balanus laevis differs from all other cirripedes in having the basis filled up with a cancellated structure; the extent to which this is effected is very variable & very often there is no trace whatever of this remarkable structure. In Chthamalus antennatus the third pair of cirri (legs) is very remarkable in having one of the rami wonderfully elongated & apparently developed to act as an antenna; but this elongation of the one ramus & the number of its segments, was are marvellously variable; in one specimen there was not a trace of this structure; in a; & the arrangement of the spines, which are generally of functional importance & generally constant, was equally or even more variable, being arranged

(62

(Ch. 7. Cases of abnormal develop. variable)

on two distinct plans. Acasta sulcata is highly unique in having the front edge of the pedicel of the fourth cirrus developed into most beautiful, curved, prehensile teeth; but of this remarkable structure there was not a trace in some specimens from the same district which after the most careful examination I am fully convinced are belong certainly to the same species: moreover similarly anomalous teeth on the lower segments of the cirri were also highly variable. These teeth are not mere spines but real actual modifications of the edge margin of the limb: their presence caused also the abortion of the usual moveable spines. As I look at — a strongly marked variety as not not essentially differing differently from a species, I may advance as an illustration of our law, a variety of Balanus balanoides which I at first described as a distinct species: in this the segments of the posterior cirri had ten pairs of main spines—a number quite unparalleled in any other cirripede whatever; but on examining many specimens I found the number varying from seven to ten pairs!

(63

(Ch. 7. Cases of abnormal & var. develop.)

Lastly I may advance the case of the opercular valves in Pyrgoma & in the too closely allied genus Creusia: the opercula valves, I may premise, are of the highest functional importance, & stand in direct relation to the most important muscles in the animal's body. These valves present very little slight differences in most of the genera of sessile cirripedes; but in Pyrgoma they come n widely different, as to colours differ in the most astonishing striking manner in the different species: I had not sufficient specimens in most of the species to ascertain whether they varied much as they ought to do according to our law; but in (a) Pyrgoma dentatum tha law was is fulfilled in the most extraordinary a are a more marked manner: the scutum in this species has a special ledge greatly developed;—it has the articular ridge developed into a unique tooth-like projection;—the whole outline of the tergum is most unusual & on the inner side there is a unique tooth; now all these extraordinary conformations varied

[63v]

(a) Pyrgoma cancellatum, the adductor ridge giving attachment to the great & important adductor scutorum muscle is developed in the most extraordinary wonderful & abnormal manner, & it is variable: in P. dentatum our

(64

(Ch. 7. Cases of abnormal & var. develop.)

to in so wonderful a manner, that it is no exaggeration to say that the varieties differed far more from each other in these important parts of the structure than do the other genera of sessile cirripedes in the same parts. Creusia spinulosa might be added to this list; but the variation in the opercular valves was so great & so hopelessly perplexing that after weeks of labour I had to give up in despair the determination of what to rank as species & what as varieties.*(See my monographs on the Lepadidæ & Balanidæ (p 155) published by the Ray Soc. Under the heads of the Genera & Species, above specified, full details are given.—)

(65

(Ch. 7. Cases of abnormal & var. develop.)

We Insects.— will now turn to insects. We will now turn to insects, & give some illustrations from several of the great orders. One of the most striking cases has been given to me by Mr. Wollaston, namely that of a beetle, the Eurygnathus Laterillei*a The female of which has its head presents "the extraordinary anomaly" of its head being immensely more developed than that of the male; & Mr. Wollaston believes that the case is unique unparalleled in the whole vast order of Coleoptera: now this, character though serving as a well-marked specific character, — is so excessively inconstant that "scarcely two females have their heads of exactly the same size"; in some there being only a tendency rises in this direction, in about two-thirds of the specimens, the head being "literally immense". (a) Mr. Wollaston believes that the Harpalus vividus is the only species in this great genus, which has its elytra connate, "but this character, anomalous as it is, does not alwa is far from constant uniform". In the whole genus Scarites the mandibles are in both sexes remarkably developed, compared with other Carabideous genera, & Mr. Wollaston informs that "in size they are imminently variable."—In Lucanus the

[65v]

*a Insecta Maderensia p. 20.—

[65vv]

(a) text

The females of some species of Dytiscus, which normally have their elytra deeply furrowed in a very remarkable manner, are sometimes quite without these furrows; yet such females have been caught in connection with the males.*(Westwood, Modern Classification of Insects. vol. 1 p 104)

(66

(Ch. 7. Cases of abnormal & var. development.)

In the Stag-Beetle, & indeed generally in the Lucanidæ, the mandibles in the males are, as its name expresses, enormously developed & are eminently variable not only in size but in the form of the terminal teeth; yet the mandibles, as Mr. Stephens (Illustrations of British Entomology Mandibulalata. vol 3. 1830 p 367) has well remarked in ordinary cases "are dwelt upon by entomologists almost with mathematical nicety." The astonishing variability of so important an organ as the mandibles & of some other organs in this & in many of the following cases, is rendered very striking if the same part or organ be compared in a set of females of the very same species, where they will be found to be almost absolutely identical in form.

[For readability Darwin's horizontal and vertical crossed lines are left undeleted]

agree with mathematical nicety, Mr Wollaston has remarked to me that he believes that this great diversity in the mandibles of the Lucanidæ is owe caused by the commonest of kind of food which the larva has received, but it remains a question why this should affect an organ in the male alone, virile force Stag-beetle too imperfect & common

(Mr. White showed me a series of specimens of a magnificent Chalcosoma from the Philippines in the British Museum, in which the females were identical identical absolutely similar, but the males exhibited the

(67  

(Ch. 7. Cases of abnormal develop. variable)

most surprising series of varieties in the curious horns on the thorax & head; these horns being five or six times as large in some specimens than in others & with great diversity in the teeth: so it is in Megasoma & many Dynastidæ. So again in genera allied to Onthophagus; & so in the the males of many Scarabæidæ & of some Cetoniidæ. To turn to another quite distinct group of Coleoptera; some the males of some Staphylinidæ are horned, & the horns are very variable, as in Bledius.

(The whole snout snout is much elongated in the male Attelabus & in some Curculionidæ, & this is in them very variable as I am informed by Mr. Waterhouse. In the male of the Truffle beetle, beetle (Leiodes) the thighs are much incrassated &, here again, as I am informed by Mr. Waterhouse the [illeg]they are very variable. —In the males of Choleva, the trochanters of the hind legs are liable to great variation. (Andrew Murray, Monograph of the Genus Catops 1856 p 14-). In the carrion feeding Necrodes littoralis, the males have incrassated & dentated femora, enlarged increased tibiæ

(68

(Ch. 7. Cases of abnormal develop. variable)

dilated tarsi, sculptured thorax, costated elytra, & everyone of these points is highly variable! (Stephens Illustration of British Entomology vol 3. p. 367)

To turn to another Order, the Homoptera: the Umbonia spinosa was pointed out to me by Mr. White as having most singular spinose projections of the thorax, in both sexes, & these are highly variable. Again in Fulgora or the Lantern-Fly & in the Fulgoridæ the forehead is most singularly dilated into a muzzle, sometimes even equalling the whole rest of the body in length! this strange projection differs greatly in the different species,*a is not confined to either sex, & is very variable in several species, as I saw in specimens shown me by Mr. White.

Lastly to take one other great order, of the Hymenoptera, in which I am indebted to the highest authority Mr. F. Smith, for some good the following striking illustrations of highly abnormal characters in several species, & which being, as heretofore, we shall find to be very highly variable. In both Both sexes of the Chrysis ignita (Entomologists Annual 1857)  are highly peculiar is remarkable from the apex of the abdomen being armed with four  teet teeth;

[68v]

 *Westwood Modem Classification of Insects vol 2. p 428.

(69

(Ch. 7. Cases of abnormal develop. variable)

but that these are so variable in length as well as in position, as to assume nine distinct types of form, & are occasionally nearly or quite absent!

In a Bees, the The male of two of a of about Andrena longipes, is one in some examples, but not in all, has an enormously large head in comparison with that of the female: in another species, Andrena fulva, large males have a long acute tooth at the base of the mandibles, but in smaller specimens this is reduced to a mere tubercle; & this form was consequently described by Kirby as a distinct species. In a male Saw-fly, the Tenthredo femorata, a series of specimens "exhibits a wonderful difference in the development of the posterior femora." in the males" On the other hand the females of the two following Bees are have a remarkable peculiarity very remarkable & confined to two or three species in their respective genera: namely in the Osmia fulva, two stout horns on the front of the head, & these vary greatly in length & shape, being somewhat bifurcated when large & wedge-shaped when small; & secondly in the Nomada lineola, two teeth on the labrum, & these vary so much in length

[70a]

good,*(the case in fact is the same) when all the that several species in the same genus differ greatly from each other in some part, usually constant generally uniform in the Family,— as with the opercular valves in Pyrgoma

[70av]

good, when one species differs remarkably in some parts from all the others in the same group a single & when all the species of a group differ somewhat from each other in some part, as with the opercular valves in Pyrgoma; usually are generally uniform in the Family,— as when a single species differs somewhat in some part from its congeners.—indeed the cases do not essentially differ from each other.

As genera are mere conventional groups, I should have expected that when a set of genera were closely allied but yet one of these genera or all differed from each other in some one respect one organ to a marvellous degree from the other genera that this part organ or part would have been variable in all the species of the such genera. This, I think does happen sometimes, but certainly very far from not always. Thus in amongst the Homopterous Insects for instance in the Fulgaridæ, we have numerous closely allied genera (each with several species) differing from each other in certain parts in the most extravagant & extreme & grotesque manner conceivable,—with ball-spines, bladders, lanterns such as a child might draw out from his fancy—& yet, as I saw with Mr. White in the British Museum, when Mr White these astonishing peculiarities did not vary much in the species of the several genera.

(70

(Ch. 7. Cases of abnormal develop. variable)

that the varieties have been described by Kirby as distinct species.(a)

(Lead)

[faint pencil note:] see pencil note at end of p. 75

In considering the foregoing facts, & others might have been added, we see that they fall under three heads, namely of some striking peculiarity being eminently variable, when attached to both sexes, or when attached exclusively to the male sex, which is perhaps the commonest case, or exclusively to the female sex. The cases seem to me far too numerous & striking to be accounted for by the mere chance coincidence of variability & unusually great development; more especially when we bear in mind how remarkably constant in character many of the very same organs or parts are when not developed in any extraordinary manner in the above cases throughout the same groups Families, in which the very same part organs or part become excessively variable when developed in a very unusual manner. in the other species of the same groups. Our laws seem to hold equally

[For readability Darwin's horizontal and vertical crossed lines are left undeleted]

good, & the case in fact is the same when a single species differs greatly in some part, one one or a few few characters part or organs from all the other species in the same genus or even somehow in the closely allied genera; on and when all the species thus differ greatly from each other greatly, in some one part or character one part. or in a few characters a genus in many contain Homoptera opposed

[70vv]

F. Brauer advances in favour of the law as given in the Origin (Verhand. Zoolog. Bot. Gesell Gesell. in Wien. 1867 Dec. 4th) the some highly peculiar characters in the wings of the dimorphic females of the Neuropterous genus Neurothemis.

(71

(Ch. 7. abnormal develop. variable)

(Mr. Waterhouse believes that the extreme diversity in the development of the mandibles & horns in the Lucanidæ & Dynastidæ is related to the state of the food of the manner in which the insect in its larval; but the question remains why the mandibles should be especially affected, it is the one sex alone. state has been nourished; & it deserves notice that in some species, for instance in the Angosoma centaurus there is, as I have been informed by Mr. White, much less variability than in the allied species. In the Lucanidæ & allied families, the existence of males presenting a wide range of varieties in their secondary sexual male characters, from extreme development to a close approach to the female condition, is so very general, that a collector is not satisfied, as I am informed by Mr. Waterhouse, until he possesses a complete series of this kind for each species; & this fact perhaps does indicate that there is here something different & quite unknown & different from the other cases of variation & abnormal development, being highly variable. One is at first strongly tempted to explain all these cases of variability in the secondary male sexual characters by the hypothesis of a great diversity in the regard take virile force of the males; on the same principle that the horns of deer are affected by emasculation, by the amount of food,

(72

(Ch. 7. abnormal develop. variable)

by amount of nutritious food or by unnatural conditions as a voyage

[pencil insertion illeg] as confinement on shipboard; (a) But the an analogous hypothesis, would be rather bold when applied to the several cases of variation in remarkable developments, characteristic of & highly variable in the female sex: in the Eurygnathus we should have to suppose that about one-third of the individuals females, namely those with small heads like nearly like those of the males, were in some degree sterile. Moreover this view is clearly inapplicable to abnormal characters in no way. connected with sexual function, & common to the two sexes as in many birds & as in the hermaphrodite cirripedes, which have afforded us so many instances of female parts unusually developed being highly variable.

But now let us turn to what we know in regard to domestic varieties: we have seen in our two first chapters that fancy breeds, —those which the fanciers are now improving by selection to their utmost,—are much more difficult to breed true or vary more in the particular admired & selected points, than breeds which have long inhabited any district without

[72v]

(o)

; and I think this explanation may must may be true to a large extent.*

 * We must, however, be cautious in inferring loss of virile powers from loss of the secondary male characters; to give one instance; Sebright Bantam has not sickle-feathers in the tail, yet a writer in Poultry Chronicle, shows that one thus deficient, was the father of an [innumerable] number of chickens.

Hewitt says they are generally deficient in virile force Hen-tailed Game Cocks show no loss of virile powers.

(73

(s Ch. 7. abnormal develop. variable)

particular care having been paid to them; I refer of course a to pure breeds alone & not to fluctuating mongrel mongrel crossed breeds which would necessarily be variable from crossing. For example compare the head & beak of the common & improved Tumbler, of the common & improved carrier, with these hardest beaks of same parts parts in any old breed, as the Fan-tail, in which these point points have not been much attended to, & observewhat an note the how vast a fact astonishing range of variation the head & beak present in the two former cases. in directly opposite ways. The cause seems obvious, namely that in each of the later generations, individuals with certain admired points most strongly developed have been selected, so that the particular characters in question, though the difference in each generation may have been so slight as to have been scarcely appreciable, have not been fixed by strict inheritance during a long course of centuries. Moreover we have seen in our first chapters that new characters, or those in course of improvement through Selection often become, from quite unknown causes, attached in a greater or lesser degree to one sex, far

(74

(Ch. 7. abnormal develop. variable)

most generally the male sex,—take for an instance the wattle in the improved carrier Pigeon; furthermore it would appear that those characters which become under domestication attached to one sex, are eminently variable.

Now if we look at species as only strongly marked & very permanent varieties, & consequently at all the species of a small group, as the descendants from some one form,—like the fancy pigeons from the Dovecot,—then those parts in which all the species agree will have been inherited by them for an enormous period, by the breed those & ought to have a be thoroughily fixed in the breed: in such cases it will make no difference whether or not very fixed characters: on the other hand the part for instance is developed like a Bat's wing, in an extraordinary manner: on the other hand any part or organs developed in an extraordinary degree or manner compared with the same part in the closely allied species, according to our theory, will have undergone an very immensely long course of modification through natural selection within a comparatively recent

(75

(Ch. 7. abnormal va develop. variable)

period; for as natural selection acts only by the addition of successive very extremely small changes, & as the part in question is supp is developed in an extraordinary degree or manner, the process of addition must have required a very long time to have produced the given result; & all this must have taken place since the several species branched off from the common parent stock & therefore long subsequently to any considerable change in the other parts of their organization. of one the several species. Consequently, in accordance with the analogy of our improved domestic fancy breeds, we might have expected that such parts or organs to be the least fixed or most variable of the whole organization. would be the least strictly inherited, with a strong tendency to reversion to the aboriginal parent form. & altogether Moreover we might have expected from the same analogy, that some of the [lately]comparatively late & extraordinary developments would have to become attached to either sex, & generally to the male sex, without as far as we can see profiting either sex; & furthermore we might have expected all their that such secondary sexual characters would have been especially evidently highly

(76

(Ch. 7. abnormal Develop. variable)

variable,—all facts which seem to hold good in nature. Nor we must forget that Sexual Selection, by which the secondary characters are structures of the male is modified

variations in the secondary characters confined to the males alone, & useful to them in their struggle for the females are added up & accumulated struggle with other males for the females, is less rigid than ordinary selection; the less successful males generally leaving some offspring; so that those secondary sexual characters which are of use to the male, would be less rigidly scrutinised & sifted than the characters on which the life or death of the individual male & female depended.

On the other hand, if we look to the generally accepted view doctrine of each species having been produced by an act of creation, I can see no explanation of the several facts given in the present section, that showing that secondary sexual characters, especially if developed in an extreme degree, & generally that all parts developed in any very extraordinary manner, are apt to be highly variable.

(77

(Ch. 7. Rudimentary parts, variable)

A part so little developed, as to be called rudimentary, tends to be highly variable.

The subject of Rudimentary organs will be treated of in one a separate chapter; I refer here to this one point of variability here, as standing in relation to our last proposition of parts developed in an extraordinarily great degree being variable. The cause, however, I believe to be different: organs become rudimentary through disuse (aided, perhaps, by the principle of compensation & sometimes often by natural selection) & through the its the effect of disuse of disuse becoming hereditary at a corresponding period of life corresponding with that of the disuse. Disuse shows of course that the part in question is not useful to the Species, & therefore natural selection cannot come into play to keep fixed a a part when become useless & rudimentary part, to a fixed cha, namely by rejecting all destroying all injurious departures from its one fixed order type. The continued existence of a rudimentary organ depends wholly on the strong principle of inheritance, as we shall, hereafter,

(78

(Ch. 7. Rudimentary parts variable)

[pencil insertion:] its variability from natural selection no longer watching its variation

attempt more fully to explain. On the other hand, a part developed in an extraordinarily high degree is as I suppose variable, as we have just seen, from not having become strictly inheritable,—from natural selection not having had time sufficient to overcome the tendency to reversion & to fix & regulate its own work of addition of adding up very many small successive modifications.—

[pencil note:]The diverse branching of horns in Lucanidae & the nine types of abdominal points in Chrysis, shows not all reversion—there is fluctuation as well as reversion.

(79

(Ch. 7. Monstrosities)

Monstrosities: arrests of development. —As monstrosities are can not be clearly distinguished by any clear line of derivation from variations, I must say a few words on some of the conclusions arrived at by those who have studied the subject. In Isidore Geoffroy St. Hilaire & his son Isidore (Principes de Phil. Zoolog. 1830 p. 215. And Histoire des Anomalies 1836 Tom. 3. p. 437 et passim Tom I 111) repeatedly insist on the law that suppresses monstrosities in one animal represents the resemble normal structures in another. So in the vegetable Kingdom M. Moquin-Tandon came to a similar conclusion, & says, "Entre une fleur monstrueuse et une fleur normale it n'y a souvent d'autre difference que l'état accidentel de la premiere et l'état habituel de la seconde. La monstrosité est done en general, l'application insolite a un individu ou a un appareil, de la structure normale d'un autre individu." (Elements de Teratologie vegetale p. 116 p. 342. The same view is taken by M. Auguste St. Hilaire in his Morphologie Vegetale p. 818)

As the resemblance between a monstrosity & a normal structure is generally not very close, & as the comparison is often made with forms fro remote in the scale of nature, & as when all within the same great class

(80

(Ch. 7. Monstrosities)

are included, a vast field for comparison is opened, I cannot avoid the suspicion that some of the resemblances given are simply accidental. But I imagine no one would account for all the resemblances on the doctrine of chance. To give two or three of the best instances from Mr. Isidore Geoffroy;—in the pig, in which has the snout in much developed & which includes in the same class in allied to the Tapir is allied, but, as Owen has shown, not so closely as we formerly thought to the Tapir & Elephant, a monstrous trunk is developed oftener than in any other animal: as most mammals have more than two breasts the frequent monstrosity of three, four or even a greater number of mammæ breasts in woman seems to stand in relation to the normal structure of fact of most mammals having more greater number than two mammæ: Carps are very subject to a curious monstrosity causing their heads to appear as if truncated, & an almost exactly similar but normal structure is met with in the species of Mormyrus, a genus of fish belonging to the same great Order with the carp.*(Histoire des Anomalies Tom I. p 285. Tom 3. p. 353. p. 436). Notwithstanding such facts, &

(81

(Ch. 7. Monstrosities)

many others could be given from the animal & vegetable Kingdoms, I cannot believe that in a state of nature new species arise from changes of structure in old species so great & sudden as to deserve to be called monstrosities. Had this been so, we should have had monstrosities produced closely resembling other species of the same genus or family; as it is comparisons are instituted with distant members of the same great order or even class, seem picked out, as if by chance, for comparison appearing as if picked out almost by chance.

Nor can we I believe that structures could arise from any sudden & great change of structure could arise (excepting possibly in rarest instances) so beautifully adapted as we know them to be, to the extraordinarily complex conditions of existence against which every species has to struggle, as we know every part & organ to be adapted:

Every part of the machinery of life seems to have been slowly & cautiously modelled to guard against the innumerable contingencies to which it must be has to be exposed.—

As all vertebrate animals, for instance, pass

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(Ch. 7. Monstrosities)

through nearly similar embryonic changes, we can see that arrests in the development of any part,—a doctrine on which M. Isidore Geoffroy lays much stress— will account for a certain degree of resemblance of many monstrosities to the normal structure of other animals, even when very remote in the same great class. It by no means follows from this that the normal structure should even have. A very frequent monstrosity in flowers flower plants having irregular flowers, such as Snap-dragons, is their becoming regular; & as such flowers are known to be regular as if as a in their early bud state, I presume that this monstrosity called peloria would be admitted to be an arrest of development; as an instance of how all monstrosities are governed by laws, it may be added that the peloric flowers nearest the axis are much the most apt to become regular; *thus I have seen a Laburnum tree with all the flowers at the end of each raceme quite open & regular not having the proper papilionaceous structure.

Other monstrosities appear caused by not exactly by arrest, but by abnormal development; thus in the case of a monstrous number of mammæ or digits, it may be surmised that in the embryo of all vertebrate

[82v]

 *Moquin-Tandon Teratologie Vegetale p. 189.

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(Ch. 7. Monstrosities)

animals there is a tendency at some very early age to produce several mammae or digits, & that this tendency from quite unknown causes of occasionally ha becomes fully developed in animals normally having only one or two or four some small number. whether or not There are other monstrosities

[For readability Darwin's horizontal and vertical crossed lines are left undeleted]

are common to very different animals, without even appearing in any species as a normal state, or they are now appear in some so remote in the scale of nature from that which present the monstrosity that we can hardly suppose that seem not be explicable either by the arrest or development of any structure actually in common to the embryo connected with the doubling of parts, the union of distinct embryos &c, to which we need not here allude. And there are other monstrosities, apparently not to be explained by arrests of or abnormal increase increments of development, which are common to various animals & plants in the same great classes, & which I presume can be understood only only on the supposition of similar abnormal conditions acting on organic structures having much in common,—so created according to the common view belief, but according to our theory views due to inheritance from a common

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(Ch. 7. Monstrosities)

though sometimes immensely remote stock. I will only further remark that according to these same views, a part or organ may in one creature become normally reduced in size or quite atrophied from disuse during successive generations, in another it may be suddenly become so by in a monstrosity by an arrest of development;—again in one creature a part may become by long-continued natural selection become greatly increased in size or number, in a monstrosity it may suddenly be thus increased by abnormal development; but the possibility of this diverse origin of similar parts, through normal & through monstrous formation, evidently rests on the common embryonic structure of the two forms; & how organisms remote in the same great classes come to have a similar embryonic structure will be treated of in a future Chapter.—

M. Isidore Geoffroy Saint-Hilaire makes one generalisation which concerns us & well deserves notice&*;—

(*Histoire des Anomalies Tom. I p. 281, 418, 481 650 &c.)

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(Ch. 7. Monstrosities)

namely, that the more an organ normally differs in different species of the same group, the more subject it is to individual anomalies: thus taking the case of monstrous deplacements of organs, he affirms, that "Les organes qui se déplacent le plus fréquemment sont aussi ceux qui présentent des déviations plus considérables de la position normale"

We will now proceed to some remotely analogous considerations in regard to varieties & species.

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(Ch. 7. Varieties resemble other species)

Distinct species present analogous variations; & the a variation of one species often resembles the normal structures of an allied species: or more commonly resumes the general character of the group to which it belongs.

In the first Chapter I gave a few instances of variations produced under domestication, resembling in some character distinct species; & as some of these might be called inherited monstrosities such case can hardly be distinguished from those alluded to in our last section. Our present section relates more especially to varieties produced under nature or in organisms not much affected by domestication. But I think the bearings of our present discussion will be best shown by first giving an illustration from trifling variations in that group of domestic varieties, which I know best, namely pigeons. In all the main breeds there are analogous subvarieties, of the same similar in several colours,—in having feathered legs, & turn-crowned heads; in several of the sub-varieties of the breeds & in sub-varieties of other breeds having the the lesser wing-coverts are chequered with white & the primaries white. None of these points have any direct relation to the parent aboriginal parent breed, the Rock-Pigeon; it is a curious yet, I think presume, that think it

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(Ch. 7. Varieties resemble other species)

no one will cannot be doubted that these analogous varieties are due to the several breeds their having inherited an a like common organization in from a common source origin; & this being similarly this organization having been acted on by similar organic & inorganic causes of change: In the same way as just as we know that children of the same family often show a remarkable parallelism in symptoms when suffering from the same disease.

[faint pencil note:] (Sir H. Holland

Some of these variations as feathered feet, chequered wing-coverts &c are fixed in & characteristic of certain breeds & sub-breeds; therefore when such character appears as a chance for the first time in one a breed, the sub-breed thus characterised presents an analogy to th other breeds properly so characterised. On the other hand when a breed repeatedly so characterised, thus an individual without one of the above characters character of the above kind is lost; or to give another instance when a blue Pouter which has ought to have all its primaries white is "sword-flighted" that is has some of the first primaries coloured,—or when a Turbit which should have a white tail throws a dark tail*(of which Mr. Tegetmeier has had an instance) these

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(Ch. 7. Varieties present resemble other species)

[For readability Darwin's vertical crossed lines are left undeleted]

& inexplicable fact that some of these characters are brought out by crossing distinct birds of distinct breeds not having so characterised.

[87v]

*I may remark that in crossing various breeds I have clearly noticed that colour sticks to the caudal feathers than to any other part, & secondly to the few first primaries: I have repeatedly noticed in crossing black & white birds of very different breeds, the few first primaries are black, succeeded by white feathers

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(Ch. 7. Varieties resemble other species)

are not new variations, but rather the partial reversions to the parent breed but not to the parent species. Of most reversions to the aboriginal species I have given an excellent instance in my discussion on Pigeons, in the fact that all breeds have occasionally throw blue birds, & that these always have the two black bars on the wing, generally a white rump & a white edgings external web to the exterior caudal feathers, —all characteristics of the aboriginal Rock Pigeons. It deserves, as we shall presently see, especial notice that these just specified characters are frequently brought out by crossing two Pigeons neither of which possess them are blue, or probably have had a blue bird in their race for several many generations: why the disturbance caused by a cross should have this effect we are perfectly ignorant.

In respect to all cases of reversions to ancestral characters, I may revert to the only hypothesis which appears to me tenable; namely that in such cases the child does not in truth resemble its ancestor a hundred or thousand generations back more than its immediate father, but that in each generation there has

(89  

(Ch. 7. Varieties resembling other species)

been a tendency to produce the character in question, & that this tendency at last for causes of which we are profoundly ignorant overmasters the causes which have for so long rendered it latent. This does not seem to me more surprising than that the merest rudiment or vestige of an organ should be inherited for numberless generations. Those who explain th an abnormal & monstrous number of mammæ in a woman from the fact of the number of mammæ in vertebrate animals being generally greater than two, must will admit that a tendency, as well as an actual rudiment, may be inherited for any length of time. [pencil note:] Under this point of view reversion to an ancestral form is only an arrest of development,—or the appearance in the mature state of a character which ought to have been passed through in an earlier stage. [in margin:] Snap-dragon

Supposing that we had t reason to believe that all the breeds of pigeons had descended from one stock, but did not in the least know what its characters were, or the ancient character of any of the breeds we should be inspirequite perplexed to conjecture, when an individual was born with a turn-crown whether this was a case of reversion of a character formerly attached to the breed, or a new variation analogous to what had appeared

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(Ch. 7. Varieties resembling other species)

at some former period appeared in & become fixed in some other breed. In the case, however, of the blue birds, as so many particular characters appear together without, as far as we can see, any necessary correlation, (a text) that we might have pretty safely inferred that the black wing bars, white rump &c were due to reversion.

But whether, or not, we could tell which was reversion characters were due to reversions (either to the aboriginal form or species or to some subsequent but ancient breed) & which to new variations analogous to those alwa of already existing in other breeds or sub-breeds, we should without hesitation put all down to a community of organisation from common descent.*

Now let us turn to nature; we have frequent instances of distinct species & strongly marked natural varieties races, presenting analogous variations. Thus many Foxes, as C. lagopus, fulvus & vulpes present crucigerous varieties; (Sir J. Richardson Fauna Boreali-Americana p. 84, 93.): the American &

[90v]

*Those who believe, as I do, that our hens something is Fowls are all descended from the Gallus Bankiva have an analogous case in so many breeds, as was remarked to me by Mr. Tegetmeier, having sub-breeds with their feathers laced edged or laced & per other pencilled sub-breeds with their feathers transversely barred or pencilled. This latter character may be derived from the hen of the G. Bankiva (though transferred to the Cocks of some of our breeds) & may be ranked as a case of reversion;

It is doubtful whether either class of colour-marking can be attributed to reversion but the both the lace edging or the lacing, & pencilling a character noticeable in some other species Gallinaceæ, must be considered as a are variations analogous in one sub breed to another, & likewise to some other quite distinct species of Gallinaceæ.

[90v2]

(a) & as these characters arise character appear from a crossing of distinct breeds,—a cause wholly unlike what must aboriginally give the blue colour—

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(Ch. 7. Vars resembling species)

Europæan Bears both sometime have young with a white collar. (Id. p. 15). So in our the British Bush brambles, our best authority (Dr. Bell Salter in Henfreys Bot. Gazette vol 2. p. 114) says "nearly allied species are apt to sport in parallel varieties .... so that the species being ascertained, the same designation & very nearly the same description will characterise the variety in each case": these nearly allied species are themselves looked upon by many Botanists as strongly inherited races.

(See the account by Mr. Ed. Lees on Brambles coming true from seed, in Phytologist vol. 3. p. 54) An excellent observer in Sweden, Andersson (Henfrey Bot. Gazette vol 2. p. 251) describes a set of varieties (which have been mistaken for described as species) of Carex ampullacea & vesicaria, which "present a perfect analogy of every form in one species to those of the other."

As I look at species as only strongly marked varieties, I may adduce one other, but distinct case, namely the remarkable correspondence, as insisted on by Prof. Fries (Bot. Gazette vol 2. p. 185) between

[92A]

Stoat case

Loudon Magazine

vol 7. 504-591

— 5 294-718

— 8 31 {Thus stoat turning white in Cornwall strongest case.

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(Ch. 7. Vars resembling species)

indirect evidence. Thus the British Stoat (Putorius ermineus) may be called a variety in as much as it does not regularly turn white in winter: it has inhabited this country since the Glacial period, (Owen, British Fossil Mammals p. 116), & during that period, analogy will now from other countries could lead everyone to can leave no doubt that it was always white in winter. (Blyth remark in Loudon vol. 8. p 50—makes me doubt the case—see about Irish Hare & then give up case if Hare turns allude to it—)

Bell seems to think common in North—

Will not do to quote, without Variable Hare offers a good case

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(Ch. 7. vars resembling species)

between particular series of the American species, will of Hieracium, with those of Europe. Now in all these such cases, those who believe in independent creations of parallelism of variation would be ordinarily accounted for by the species having been created with a closely nearly similar organization: following the analogy of our domestic productions we should attribute it to community of descent.

If for instance there had been a permanently crucigerous species of Fox (as some believe there is), then the crucigerous variety of another species would have been a case of variation analogous to another a distinct species; so would it have been if our supposed crucigerous species had produced a variety without the cross. As we do not know the ancestors of organisms in a state of nature, whether ranked as varieties or species, we can very seldom tell whether their varieties, when resembling in character other species of the genus, are variations for the first time in the breed, or reversions to a state through which the species in question had formerly passed. But in some very few cases we can form a pretty good from indirect evidence a conjecture on this head.

Unfortunately we have seldom evidence for crossing

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(Ch. 7. vars resembling species)

(I will now give in small type such cases as I have collected illustrative of one or a few species varying in a manner closely analogous to other & distinct but allied species of the same group.—I may recall to mind my former remark on the difficulty of collecting such cases excepting by each the an author himself carefully going through the group with which he is most familiar. I think that the following cases are too numerous & precise to be accounted for by mere chance, more especially as the comparison is always made with allied species, generally closely allied species. (It has several times occurred to me in reading an account of a set of species of the same genus which have differed in some remarkable respects character, that I have truly predicted that I should find this same character described as variable in the individuals of some of the species.) In the list of cases of parts greatly or abnormally developed being highly variable, in so far as the variations bring back the species to the common type of the genus they might have been here introduced. All the cases, alluded to in Chapter 4 of inter varieties intermediate between two species, whether the one or both vary, in fact come under this head. And of variations of what systematists consider

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(Ch. 7. vars. analogous to other species)

trifling characters, innumerable characters, as colour, size, proportion being analogous to other species of the same genus, innumerable instances could be given,—indeed a large part of the difficulty in identifying species seems due to varieties approaching in character other species—but in such cases it seems hardly possible to distinguish mere general variability, from variations having some direct relation to the structure of other species of the group. But as far as they go they confirm what I must consider a law, namely that variations whether in some degree permanent, or quite fleet occurring only in single specimens of one species often assume the character of another species of the same group.

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Small type

Prof. Vaucher shows (in Mém. Soc. Phy de Genève Tom. I. p. 300) that the modes of gemmation are constant in each genus with some few exceptions; but in the g for instance, the species of Syringa two species have a different kind bred in two ways; & in in the common Lilac the two f modes of gemmation are sometimes seen even in the same bush.—

Decandolle states (in Mem. Soc. Phys. de Geneve Tom. 3. Part II. p. 67) that in the Lythraceæ some of the very natural genera have some species with petals & some without; & that in Peplis portula the individuals indifferently have petals or none.—

In the Primulaceæ, according to M. Duby (mem soc. Phys. de Geneve. Tom. x. p 406) Samolus is the only genus in which the ovary is adherent to the calyx; but and in one species of another genus in this family, though not very closely allied namely Cyclamen, some individuals of one of the species have the ovary partially adherent.

(76

[This is a discarded note for page 76. Is has been re-written. See pp. 317-18, Laws of variation]

(Ch. 7. Abnormal develop. variable)

variable,—all facts which seem to hold good in nature. (a) On the view of each species having been independently produced by an act of creation, I cannot see any no explanation of the several facts above given in the present section or showing the the great variability of a part or organs abnormally developed secondary sexual characters especially if developed in a extreme degree & generally of that all parts developed is very very extraordinary manner, are apt to be highly variable.—

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Oxalis buplevrifolia has simple & lineal leaves unlike al all the other species of the genus, but Aug. St. Hilaire found some individuals with this enlarged petiole surmounted by the three small usual, though here small leaves. (Morphologie Vegetale p 143)

The alternation & opposition of the leaves is respectively constant throughout many great Families, but in the Salicariæ & Polygaleæ the several species, & often even the individuals of the same species, have either alternate or opposite leaves; & both often are found even on the same individual. (Aug. St Hilaire Morphologie Vegetale p. 183) (a)

The torsion in the æstivation of the corolla is no was thought to be uniform in the Gentianaceae, but in Gentiana Moorcroftiana & Caucasica it is different from the rest of the family & in the individuals of the latter species, it is found to vary in the individuals (Decandolle in Annal. des Science Nat. 3d Series Botany Tom I p. 259)

(96 bis

In the Malpighiaceæ, A. de Jussieu (Archives du Museum d'hist. Nat. Tom 3. p 86) says the leaves are always opposed, with the single exception of Acridocarpus; & even in this genus one may sometimes remark a tendency, especially in the lower leaves, & even a complete return to opposition

Decandolle has seen a variety of Geranium pratense (mém soc. Phys. de Genève Tom 1. p 443) with the two upper petals white & the three lower blue; "on retrouve ici dans les Geraniées à fleurs régulières, cette tendence a la disparité des petales si remarkables dans plusieurs Pelargoniens". Geranium & Pelargonium, as every one knows, are very closely related genera.—

(97

Aug. St. Hilaire (Mem. du Mus. d'Hist. Nat. Tom XI. p 49) says that according to Adamson there ovary has been described as tartal unilocularis at tartal 3-locularies & that tho in the different species of Helianthemum one may observe "toutes les nuances possibles entre le plancenta purement parietal et des loge loges parfaitement distinctes", & that "dans l' H. mutabile une lame, plus ou moins large, s'etend entre le pericarpe et le placenta"; so that in this species the separate degree of division of the ovary into lodges seems to be variable. in this species.

In the Compositæ the presence of a ray to the outer florets is generally a constant character; but in Senecio, for instance, some of the species have a ray & some not; & of those species which have not, as the S. vulgaris, varieties are found with having a small ray; on the other hand in the species ordinarily having a ray, as S. Jacobæa, varieties are sometimes found without a ray

(4 98

[pencil note:] rule holds in crossing

W. Herbert (Amaryllidaceæ p 363) crossed says that by crossing Calceolaria arachnoeides which is purple with C. corymbosa, which has small purple specks on the yellow corolla, flowers were produced to the surprise of cultivators broadly blotched with dark & even blackish purple "but the subsequent discovery of a Chilian biennial species, which I shall call C. discolor, blotched with a reddish purple in a manner somewhat similar, shewed that such an arrangement of the colour was a natural variation of the genus, which the cultivator might therefore have expected, if all the natural species thereof had been previously known."

Nerine curvifolia fertilised by a hybrid curvifolia-pulchella, produced seedlings, of which one produced a young crimson leaf, "which I have never seen in the genus,"

"such a remarkable seminal variation brings curvifolia in closer affinity with N. marginata, which is distinguished by a red margin to the leaf". (Herbert Amaryllidaceæ p. 412)

(5 99

Gærtner says that (Bastarderzeugung p. 50) that Lychnis diurna when growing in dry places sometimes has sharp teeth on the sides of the petal, as is the case with Lychnis flos cuculi. I may add (a)

Azalea with five stamens & Rhododendron with ten stamens, of which half are of inferior power are closely allied genera as everyone may see; the latter has & W. Herbert says (Journal of Horticultural Soc. vol 2, p. 86) he has frequently raised seedlings of A. Pontica & Indica with frequently producing with 7, 8, or 9 stamens. Azalea nudiflora in N. America presents "numberless varieties some of them exhibiting ten or more stamens". Asa Gray Manual, p. 257 2nd Edit.

(The northern species of Gladiolus present, according to Herbert, (Journal of Hort. Soc. vol 2, p 90) "a strange diversity of seed"; having there being a winged or foliaceous margin in some of the species, which in totally disappears in other species; & in G. communis some varieties have it curtailed, & some almost obsolete.

Of the Oak genus some species are evergreen & some dioiduous; & the varieties of Quercus cerris are so variable in this respect, that Loudon (Arboretum et Fruticetum vol 3. p. 1846) says its varieties "may be arranged as deciduous, sub-evergreen & evergreen."—So it is with the genus Berberis. (Hooker Flora Indica p. 218)

[99v]

(a) that I have seen a seedling Spanish Pink D. Hispanicus with its petals so deeply cut & the point so much elongated, as to call to mind the all petals of Dianthus superbus.—

[100a]

5

Lindley put their genera in remote not Fam.!!

Hooker's Misc 3/109. Mr. W. Wilson says the Andromeda polifolia like Vaccinium vitis idea sometimes has the stamens attached to the corolla.

[Abstract of Hooker's Miscellany 3: 109, CUL-DAR11.1.100a]

(6 100

Moquin-Tandon (Teratologie Vegetale p 138) says he has found a plant of Solanum dulcamara in which all the upper flowers had two or three stamens "beaucoup plus longues et plus grosses que les autres", & in S. tridynamum & Amazonium three stamens are habitually much larger than more developed than the others.

[pencil note:]Here the winding of Solanumcome into play

Dr. Hooker. (Journal of the Linnean Soc. vol. 2. p 5 Bot.) believes that the Lobeliaceæ ought to be included as merely a tribe of the Campanulaceæ.

For in the Lobeliaceæ, "even the irregular corolla affords no good mark, for some states of the Wahlenbergia saxicola (one of Campanulaceæ) have an oblique corolla, & unequal inclined anthers, of which two have the connective produced into an appendix, thus imitating a prevalent feature of the Lobeliaceæ." The coincidence of these several imitative characters seem deserves attention.—

(7 101

The American wolf is generally esteemed a distinct species from the European: Sir J. Richardson says (Fauna Fauna Boreali-Americana. Quadrupeds p. 76) its "genealogy are destitute "the black mark above the wrist which characterises the European wolf is visible in some American wolves but not in all".

The Didelphys Azarae has a broad black stripe on the forehead; & the D. crancrivora has their an indistinct dusky line; the D. Virginiana has occasionally "a small dusky stripe on the forehead (G. R. Waterhouse,— Marsupialia in Naturalist Library 1841. p. 84)

The genus Timalia (allied to the Thrushes) according to Swainson (Fauna Boreali-Americana. Birds p 31) stands in a group in which the bill is either notched or entire,— a character generally of high importance; & in Timalia pileata some individuals "have the bill perfectly entire, some slightly, & others distinctly notched; all apparently being old birds, full plumaged, & not differing in the slightest degree in other respects".

(8 102

Yarrell has stated that the Little Ringed Plover (Charadrius minor) can always be distinguished from Ch. hiaticula by a dusky spot on the inner web of the outer tail-feather; this feather being in C. hiaticula wholly white, but Mr. Garrett & Thompson have shown that this spot does occur in some specimens. (Nat. Hist. of Ireland: Birds: vol. 2. p. 103

The position of the Spleen varies differs much in various serpents, "so as sometimes to occur at a distance from the pancreas & isolated at the posterior surface of the stomach"; and H. Schlegel (Essay on Serpents. Engl. Translat. 1843 p. 55) says he has observed individual variations in this respect.—

(9 103

Tha Mr. Wollaston remarks (Variation of species p. 62) that "it is almost diagnostic of the genus Gymnaetron that its representatives should be thus (ie with blood-red dashes on the elytra) ornamented typically, or else that those species which are normally black should, when they vary, keep in view, as it were, this principle for their wanderers to subscribe to".

Mr. Waterhouse informs me that the Pachyrhynchus orbifer one of the splendid Curculionidæ of the Philippine Archipelago, which is the most variable of the group genus, in its variations typifies the regular markings of the other species. So again in varieties of Cicindela campestris the golden marks became united as in C. sylvicola; & on the other hand in varieties of this latter species the marks become disunited as in C. campestris.

The classification of the Fossorial Hymenoptera was mainly founded by Jurine Jurine on the neuration of the wings, & this has been adopted by all subsequent writers; but in Typhia & more especially in Pompilus, there is a considerable difference in this respect between the species, & in some of these species there are even individual variations (Shuckard on Fossorial Hymenoptera 1837, p. 48, 40, 43.)

(10 104

Lastly I will now give some examples from cirripedes. Acasta fenestrata, & in a lesser degree A. purpurata present a very remarkable character (Darwin Balanidæ p. 305) in the shell being perforated by six clefts or holes in the lines of suture; & we have a similar character in some varieties of A. sulcata. In genus the different species of Pyrgoma, the opercular valves on each side are sometimes quite separate & sometimes so perfectly calcified together that even the line of juncture cannot be distinguished; & in P. milleporæ the degree of union (p. 368 idem) is very variable in different individuals. In Bal. improvisus (p. 251 id.) certain varieties have their terga closely imitating the form of the same valve in the allied B. eburneus: so again a very remarkable variety of the common Balanus balanoides is the form of the tergum & in the parietes being tubular makes a close approach (p. 275 ib) to the very distinct B. cariosus. Certain varieties (p. 453 ib) of Chthamalus stellatus & cirratus have the anterior ramus of the third pair of cirri elongated & antenniform, prefiguring, as it were, the remarkable structure of this same cirrus in Ch. antennatus.

[104v]

I will now give several examples from cirripedes.

Chthamalus Hembeli presents a unique character in the [illeg] walls of the old shell, when old, growing inwards & replacing the basis (Darwin Balanidæ p. 450)

(105

(Large type Ch. 7 (Ch. 7. vars. resembling species)

Lastly I will give in rather more detail the case which has interested me most, & which combines several considerations. The common Donkey sometimes is destitute, even when not an albino, of the characteristic transverse stripe on the shoulders (Loudon's magazine)

[105A]

[pencil note:]Martin sometimes [text excised] [4 words illeg]

It is said to have been seen in the Koulan of Pallas, now generally admitted not to be the parent of the domestic ass. (Dict. Class. d'Hist. Nat. Tom 3. p. 563). The Equo Hemionus & Hemiffusis well known to be characterized by not having the transverse cross shoulder stripe, but a trace of this stripe is asserted to appear occasionally. in (Horses, Naturalist Library by Col. H. Smith p. 318. Also E. Blyth in the India Sporting Review 1856. p. 320)

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(Ch. 7. vars. resembling species)

The Quagga, though strongly banded in the front part of the body is without stripes on the legs; but one individual individual which Lord Derby (Gleanings from the Menageries of Knowsley Hall 1850. p. 71 a splendid work by Dr. J. E. Gray) had kept alive had a few distinct zebra-like transverse bars on the hocks.) of [2 words illeg] (Lastly Again in the Horse, dun or mouse-coloured or eel-back ponys & horses invariably have (I believe) a dark stripe down the spine, as in the Hemionous, sometimes had a transverse shoulder stripe, like as in the Donkey, & sometimes have dark zebra-like bars on the legs as I have myself seen. as in the zebra I have been assured by a friend that he has seen in S. Wales an important breed of cream-coloured horses with the spinal stripe & cross-shoulder stripe bar; heard of cream coloured horses with the dorsal stripe in India & others with the transverse shoulder stripe in S. Wales & in other parts of the world. A friend has likewise informed me that he had a brownish horse with the same marks: Chesnut horse also longitudinal spinal & shoulder stripe. I have been informed by two other friends that they have seen Roans with the spinal stripe. Chesnut horses, also, of very different breeds not rarely have a dark & well defined stripe down the back. Col. Hamilton Smith, who has given numerous most curious facts on this subject, (Horses, p. xi Preface p. 109, 156 to 163, 275 280, 288. believes that the Dun Ponies have originated in a distinct, aboriginal wild race or species: they are found in Iceland, commonly (as informed by a friend) in Norway

[3 encircled 'Q's, meaning quoted]

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(Ch. 7. vars. resembling species)

Spain, banks of near the Indus, & in the great islands of the Malay Archipelago, everywhere characterized by the longitudinal stripe, occasional shoulder stripe & bars on the legs.

The It is a very ancient race, & existed (together with cream-coloured horses which we have seen also have the dorsal & shoulder stripes.) in the times of Alexander & are either truly wild or feral in the East, & were so at no very remote period in parks in Prussia. It is admitted by Col. Smith that duns appear occasionally of in herds of variously coloured horses, & Hofacker gives in two instances the colours of both parents of a mouse-coloured Horse nearly of [3 words illeg]; Col. Smith but he would account for all such cases by a cross at some time from his dun-stock; I suspect, considering the wide range & antiquity of this colour & its occurrence in wild breeds, that it might be argued with much probability that this was the aboriginal colour of the aboriginal parents all our domestic horses. However this may be, the shoulder stripe & bars on the leg are now only an occasional appearance. (a) In regard to the chesnut colour said to be strongly inheritable Col. Smith, who admits so freely various wild stocks, doubts about there having been one of this colour as it is characteristic of every breed; & Hofacker *shows that chesnuts

[pencil note:] I must see to this, for I [illeg] wrong??

(U)

[107v]

 *Ueber die Eigenschaften &c 1828. s. 12.

[107vr]

I think it wd be a very [forced explain] It wd be a hypothesis with little or no support to believe that the spinal mark on the cream colour roan,

[107v]

(a) It wd be best seems to me a bold hypothesis to attribute the spinal stripe in roan, cream colour & chesnut horses to a cross at some time with a Dun

In regard to the chesnut, horse

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are bred from both parents of different colour. The stripe is only occasionally present; it has been seen in common chesnut horses Arabians Roan common chesnut horses, in the great the heaviest dray horses of & I have seen it in a remarkably small pony from India. Hence I believe that the chesnut colour & probably the Roan itself is only as are are variations,

[faint pencil note:] not necessary due to crosses with duns & & the dorsal stripe an occasional concomitant of these colours.

Here then in the horse, Donkey, & other equine animals we have several cases under domestication & in a state of nature, of variations analogous in one variety to those in another & likewise variety & to the characters of allied species. (U)

Remembering how in how remarkable manner in pigeons the blue colour & allied tints with black wing bars &c were brought out by crossing the most distinct breeds, let us see what is the result of crossing the various species of the Horse genus. But first, let me remark that I suspect it would appear that the Dun Ponys & chesnut Horses with these asinine marks often appear from the (⸮ ⸮ ) crossing of two breeds of the Horse: this certainly is the case with the so called Kutch or Kahteawar breed (Col. H. Smith, Horses p. XI) "which are generally greys or light duns & almost invariably have the zebra marks on the legs with list down the back"; & which these are bred from a Kutch mare & an Arab sire; & it is well known asserted **(. Col. H. Smith p. 211)

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that Arabs are never duns. Now for crosses between species: Rollin (   Mr. Martin in his History of the Horse p. 212 gives a figure of a Spanish mule with the strongest zebra marks on whole length of legs: especially front legs; I have seen a fine cream-coloured mule with all four legs strongly barred asserts that the common mule between ass & Horse are particularly liable to the zebra marks on the legs.

[For readability Darwin's horizontal and vertical crossed lines are left undeleted]

Burchell's zebra (E. Burchellii) is not striped on the legs, but a cross hybrids between it & common ass in two instances were now plainly now barred on the legs. (Martin Horses p. 223. See also the splendid drawings in Dr. J. E. Gray Gleanings from the Menagerie of Knowsley Hall 1850.)  (Used)

In the Lord Morton's famous case (Philosophical Transactions. 1821. p. 20) of the hybrid from a male Quagga & a chesnut mare (not thorough bred), & in the two subsequent colts from the same mare & a black Arabian, the bars across the legs were "more strongly defined & darker than those on the legs of the quagga, which are very slightly marked": indeed it can hardly be

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said that the Quagga has ordinarily any bars on the leg. Lastly & this seems even a more curious case than the last in regard to our present subject, the Hemionus differs from the Ass in not normally having the spinal stripe but not the cross shoulder stripe & with the legs without any trace of bars but a hybrid figured in that splendid work, the Knowsley Menagerie, has all four legs with transverse bars; there are even some zebra-like stripes near the eyes, & on the shoulder there are three short cross transverse stripes. This last character reminds one of the variety of the common Ass & Koulan with a double shoulder stripe. Dr. J. E. Gray further informs me that he has seen a second hybrid quite like the one here figured. So that here we have two animals, a Here we see most plainly what an extraordinarily strong tendency there is for the bars to come out in crosses between those different species of Horse, which have naturally plain legs.

I will only further remark that in Hybrids from the zebra & ass or Hemionus in which as the one parent has striped legs, stripes on the legs might be expected, it is clear that the stripes are more plainly developed on the legs than elsewhere as may be seen in two figures in the Knowsley

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Menagerie, & still more plainly in a Hybrid figured by Mr. Geoffroy & F. Cuvier (Hist. Nat. des Mammiferes 1820. Tom I.) in which there are hardly any stripes on the legs. See again In one of these hybrids between Ass & Zebra there is a double cross shoulder stripe. (a) Again in the hybrid offspring from a Bay mare & a hybrid Ass-Zebra, the bars on the legs are to be seen, & I was assured at the Zoological gardens were extremely conspicuous when the animal was young. It may be noticed in connection with dun Ponys that in several of these hybrids, dun or slate-like colours tints prevail. (U)

What shall we say on these facts? Those who believe in the independent creation of species—& if there does exist such a thing as a species distinct from a permanent variety, undoubtedly these equine animals offer perf complete perfect examples—will say that they have been created with an organization so much in common, that under certain unnatural conditions & crosses, characters appear which mock those in animals created in other & remote situation countries: they

[111v]

In two hybrids from from the common ass with plain legs & Burchells Zebra, the legs are barred quite as plainly, perhaps rather more plainly, than in Burchells Zebra. which is very faintly barred below the knees, the legs are barred quite as plainly, perhaps rather more plainly, than in Burchells Zebra. (Gleanings from the Knowsley Menagerie; the skin there figured I have seen in the British Museum: see also Martin on the Horse p. 223)

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will have to admit that the bars on the legs of the zebra were so created & more strongly inheritable than the bars on the body; but that the similar bars occasionally appearing on the hybrid horse quagga for instance, they will have to attribute ass or on the several above hybrids are due to variation. It seems to me far more satisfactory to attribute all follow the striking analogy of domestic pigeons & attribute all the cases to one common cause, viz community of descent. Let it be observed remembered that the races of domestic Pigeons certainly differ more from each other in external appearance than do the several equine species; & that in all the races when from simple variation or crossing a blue tint appears (comparable to the dun in Horses) almost invariably the black wing-bars appear (comparable to those on the legs of the horse, ass &c) together with often accompanied by other characters, as white rump &c (comparable to shoulder stripe &c). But although these colours & markings appear in the several breeds of Pigeons the form of head & back & body &c do not alter; & so it is with the equine animals when they become occasionally striped & barred.*

From the facts previously given, it is possible that the bars & stripes on the several equine animals might be analogous variations from the

[112v]

*Mr. Martin in his History of the Horse (p. 97) has well remarked that the dun or eel-back ho Ponys are asine only in colour & not in form.

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several species having inherited a common organization, but the concurrence of several characters & more especially the characters being brought out by crossing—a cause wholly unlike that which produces the bars on the aboriginal parts facts taken together seems to me clearly to indicate reversion to an ancestral form character;(a) — or to speak more strictly this ancestral character being latent in the young of each generation & occasionally brought out when the organization is disturbed by a cross or other otherwise cause: hence, probably, it is that the stripes on the legs of the common Donkey are said to be plainest in early youth, as they were in the complex cross of Ass, Zebra & Horse. If is to my mind very interesting thus to get a glimpse into the far past, probably many millions of generations ago, & see a dun-coloured animal, with dorsal & transverse shoulder stripe, barred legs, & striped body, the common parent of the Quagga, Daur Burchell's Zebra, the Hemionus, Ass, & Horse.—

(Lead)

Finally I think the fact of varieties of one species often assuming the some character of another species as shown in the several foregoing instances,—though it is in most cases impossible for us to conjecture whether the is due to a new character variation be an old character reappearing from reversion, or a new one appearing in any creature for the first time but like what has ap previously appeared in a collateral relation owing to like causes acting on a like organization—accords well with the view that the several species of the same group, like the varieties of the same species, have descended from a common parent.

[113v]

*a This seems to have been the opinion of Rollin in     & of the Rev & Hon. W. Herbert, who in his work on the Amaryllidaceae (p. 340) alludes to the Dun Pony with dorsal stripe.

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Characters distinguishing [pencil insertion:] The distinctive character of variations are more variable than those distinguishing specific; & specific characters are species are more variable in the individually of the species than are genera the characters distinguishing genera or higher groups.—

This proposition will sound, I apprehend almost like a truism to the systematist. In regard to the variability of the character of varieties, nothing need be said, for it is self-evident. In regard to specific characters being more variable than generic many will at once assert that differences in the less important characters parts distinguish species, & in the more important parts, genera; & that the less important from affecting the welfare of the individual are more variable, than the more important parts. That this includes part of the truth I do not doubt; but in our future Chapter on classification, we shall see that some most competent judges consider that the importance of a character under a systematic point of view is not related (as we see in embryonic rudimentary parts) to its physiological importance but simply to its on its presence throughout many different forms, or in the case of species to its non-variability throughout many individuals. On the view the above In animals, I think there can be no doubt that the parts more immediately connected with the habits of life, & those more immediately exposed to external agencies, as the dermal appendages are individually the most variable parts. But characters even of this latter

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kind often present the highest degree of generality.

[pencil insertion:] Hair Owen

Look at the presence of feathers common to the whole great class of Birds: if the Ornithorhynchus had been clothed with feathers instead of hair, its place in the system of nature would not have been altered, but naturalists would have been far more surprised at the fact, than at certain important parts of the skeleton making some approach to that of a bird: and why, except from the generality of mere dermal appendages such as feathers in  being characteristic of the whole class of Birds & of that class alone?

We see the truth of our proposition in colour size & proportion of parts being the most general diagnostic characters of species, & notoriously the most variable individually. But when any the most trifling character is common to many species of a group we are surprised in the same group to find it variable in that group. If all the many species of a genus of plants had yellow flowers, we should be more surprised at one varying into red & yellow flowers, than if about half the

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species had red & half yellow. But why should this be so if we look at each species as an independent creation? But if we look at yellow & red-flowered species of the same genus as having descended from a common parent, it implies that there has been variation in this very respect since the period, generally not very remote when the species, first as mere varieties, branched off from a common stock; & as most genera have not a very high geological antiquity the period cannot have been in a geological sense very remote.

I believe that it takes an enormous period of inheritance to render any character perfectly true or free from reversion; but and anyhow as the as the descendants of a common stock will generally retain much in common, the same causes which at an early period caused the first parent varieties to assume red & yellow flowers will be apt still to react on others their offspring.

In the fourth chapter I attempted to show that every part of the organization in some group or other was occasionally variable.—But we require something more precise for our theory: in as much

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as all the species of the same genus are supposed to have descended from a common parent, it is implied that all the diagnostic characters between such species have varied within the very group in question, & within the period since they branched off from their common parent.

Generally But the very fact of the existence of a set of species, that is according to our theory strongly marked varieties, implies that the variation must have commenced long ago to allow of the accumulation of slight differences through natural selection, & therefore we have no right invariably to expect invariably to find evidence of variation in the diagnostic characters at the present day. Yet we ought sometimes, perhaps often to see discover such evidence, owing, as just stated, to new character apparently requiring an enormous period to become thoroughily fixed, & like-wise to similar causes still acting on a similar organization tending still to produce variability in the same parts. Consequently all the facts above given of varieties of one species imitating in character another

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species,—whether trifling characters not enumerated or those somewhat more striking cases which have been tabulated, & all cases of intermediate varieties & close so-called species intermediate in their whole organization, are of especial value in establishing the probability of our theory. Under this same point of view the facts before tabulated of parts or organs extraordinarily developed in single species in a group, being tending to be highly variable, may likewise be looked at as valuable, as showing within the group itself, the possibility at least of specific changes.

M. Isidore Geoffroy Saint Hilaire's proposition, before stated, that parts or organs which differ most in the same group are most subject to monstrosities, may be here alluded to. According to our theory, such parts & organs have varied much since the group of species originated, & as variations may be called slight monstrosities, we can to a certain extent understand how such parts should be particularly liable to great & sudden variations or monstrosities.

 

It would be tedious to enter into more details; but

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I believe another & related proposition could be established, namely that in those in animals presenting secondary sexual characters, the allied species generally differ in the same points in which the sexes differ. *According to our theory, secondary sexual characters are due to variations becoming primarily attached (as we see in our domestic races) to one sex & if found useful to that sex alone, being augmented & perpetuated by sexual selection; & as the part in question is thus supposed to be variable (and in a former section of this chapter I think it has been shown that secondary sexual characters are eminently variable in the individuals) we might naturally have supposed that variations of the same kind would have affected the several species of the group,—which species we look at as descendants from a common parent, just as much as we do at the male & female of the same species. Hence I believe that individual variability of any part or organ, differences in the same part in the two sexes, & likewise in the several species of the same group are all facts closely connected together & explicable on our theory

[119v]

compared the length of tail differs remarkably in the several species.—The naked & carunculated head is a specific character in the Turkey & only sexual in the allied Ceriornis.

(119n

 *note to p 119.

I will give a few facts, which have led me to this conclusion: I cd easily have added others. In most Coleoptera the joints of the tarsi offer characters of highest value: in the Engidæ, however, they exhibit numberless varieties differences, "even in the sexes of the same species" (Westwood Modern Classification, vol. i. p. 144). In the Hymenoptera Terebrantia, "the antennæ are very variable (ie differ) in the number & form of their joints both in the various species & in the sexes of the same species." (Ib. vol 2. p. 89.) we have analogous facts in the curious growing of the elytra of the females & in the different species of Dyticus (Ib. vol 1. p. 104). Shuckard in his essay on the Fossorial Hymenoptera shows that in certain genera, as Tiphia, the neuration of wings, a character of highest importance, differs in some of the species & in the sexes of certain species. Martin (in Murchison Silurian System p. 667) states that in certain Cymothadæ (Crustaceans) the males

The mandibles in the Lucanidae, & the horns in the Dynastidae differ in the males of the different species. In Deer the Horns, so eminently sexual, differ greatly in different species: in sheep in which they are more of a sexual character than in cattle, as the wild females have them either small or not at all, they vary far more in the several domestic races, or quasi-species than do the horns of cattle. The tusks of Elephants differ, a sexual character, differ greatly in the several allied genera & sub-genera & even in the races of the Indian Elephant.

In th Gallinaceous birds, the length & curvature of the tail is eminently a sexual character, & if the female of the allied genera & sub-genera be æ

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Summary. In former chapters we have seen that naturalists have no means, no golden rule, by which to distinguish varieties, whether produced under domestication or in freedom, from species.

Looking to the productions of the best-known countries, & taking the higest authorities, we often find the widest differences in opinion which form to denominate as species, & which as varieties. Isolated districts are equally favourable for the birth of varieties & species. In this chapter we have seen that although the conditions of life, as food, climate &c, seldom appear directly to cause any great modifications in structure, & must be quite important in regard to all those exquisite perfect beautiful adaptations of one organism to another; yet what slight changes the external conditions of life do produce, are analogous a in character to those characteristic of the species exposed to the same conditions. The fact of an organism varying in a like manner under widely different conditions, shows how inferior in importance the direct & immediate effects of such conditions are in comparison to the beings own organisation. to the laws of growth.

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(There seems no great difficulty in believing that those organic beings, which are so well endowed as to be enabled to beat their competitors in the struggle for life, & so thus spread, could would should soon become acclimatised through through natural selection & habits to a new climate; & if we admit this, some facts in geographical distribution & in the history of our domestic productions are explained. Though we cannot actually trace in organisms in a state of nature, the effects of disuse on structure; yet if we admit that species are mutable we can explain by disuse certain peculiarities of structure in relation to the habits of the species, as wingless birds & insects on islands, & eyeless fishes, crabs & insects animals of all kinds in dark caves & subterranean burrows: but in some such cases, it is highly probable, that natural selection may have played a part, either in reducing the structure, or in a directly opposite way by enlarging & perfecting the structures the organ, whichever tendency was at first was most profitable to the individual. beings.)

(We have seen in this chapter that the growth of the whole organic structure is correlated by many obscure laws,— so that when one as compensation, the tendency

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in homologous parts to vary in a like manner & to cohere, early the earlier developed parts affecting cohere subsequently formed parts &c.— so that if one part should be modified by through by accumulated variations accumulated through natural selection, other parts would almost certainly be likewise in consequence be modified: when flowers on the same individual plant habitually & normally differ & we see internal structural differences in their seeds produced by them, we are led moved to attribute such differences to some unknown correlation laws of growth.

In correlation of growth, all The same Similar laws of correlation, are common, as far as we can judge, are common to the production of varieties, & to the so-called creation of species.)

(Parts developed in an extraordinary manner in a species, as compared to its nearest allies, seem to be highly variable: but why should this be so, if species have been independently created? But if, in accordance with our theory, we attribute such extraordinarily developed parts to a long course of natural selection within recent times,—and this will generally have been the case, as natural selection can act only with extreme slowness, & we are comparing organisms closely allied in blood by descent & yet differing greatly

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in some one respect,—then we can understand that ext great great variability of such parts, on the same principles that the parts recently & greatly modified by artificial selection are the most variable in our domestic productions. Rudimentary parts are likewise highly variable; & why should this be so, if these rudiments were created, as we see them, in their present useless condition? Why should one species in varying so often assume some of the characters of a distinct, though allied, species? Why should the ass or dun-coloured horse be often born with stripes like those on a zebra: why should the hybrid from the ass & hemionus, both with plain legs, be strongly bu plainly conspicuously striped on the legs & even slightly on the head? Why should a variety of Geranium resemble in the colouring of its petals a Pelargonium? And a score of similar questions could be asked. If the ass, horse & zebra have descended from a common ancestor, like our domestic breeds of the Pigeon, we can to a certain extent understand the reason; but on the view of their independent creation, these facts

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seem to me a mere mockery; & I could nearly as well believe that fossil shells had been created within the solid rock, mocking the live shells on the beach.)

We admit as a truism that the distinctive characters of Varieties are apt to be highly variable; but why should the characters distinguishing species, be more variable than those, even when functionally unimportant, distinguishing genera;

[For readability Darwin's horizontal and vertical crossed lines are left undeleted]

or what is the same thing, why should the characters differing in two closely allied species be more variable, than the characters, sometimes the very same characters, distinguishing two more different sets of species:

why, for instance, should if one species plant has a blue flower & another closely allied species a one red flower, should their colour be more variable in their likely to vary in their, than in two species of the same Family one taken out of a genus with all the species blue flowered, & the other out of a genus with all having with all the species red flowered? According to our doctrines, the existence of sub-varieties presupposes

[For readability Darwin's horizontal and vertical crossed lines are left undeleted]

a a previously existing parent variety from which they have but [illeg] much in common; the existence of two within a genus & indeed of existence of all the species of the genus or in a genus presupposed a form which they exhibit much in common previously existing parent species: hence the characters

by which the sub-varieties resemble each other all differ from each other & their common parent, & those by which the closely related species

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a previously existing parent variety, from which they have inherited very much in common; the existence of two or three closely related species presupposes a previously existing parent species, as does the existence of all the several species in any genus, from which parent they have inherited much in common, but less than in the case of sub-varieties. Hence it follows that the characters, by which the sub-varieties of one variety, the two or three species of the same sub-genus, & all the species of the same genus, resemble in each case their parents, must have been inherited during a longer period than those characters in which the sub-varieties & the species differ from each other. And we have reason to suppose that mere length of inheritance tends to render characters more fixed; so that the characters inherited from the more ancient parent will tend to less or more fixed or less variable, than the characters by which the member of the same group differ from each other; or that is the distinctive characters of varieties will tend to be more variable than those of species, & the distinctive characters of species more than generic. Moreover the forms which have varied recently will often remain exposed to the same causes, which first produced the changes in their structure; & hence the same parts will often be again affected & so kept variable.

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(Why, again, in animals are the secondary sexual characters when strongly displayed so variable? if each species be an independent creation? Such sexual characters, according to our view do not differ essentially from strongly marked differences between species in all other respects most closely allied; & we have just seen that such differences tend to be highly variable from reasons already assigned. Sexual characters, moreover, have generally been accumulated by sexual selection, which is less rigid than the struggle for life & death. Sexual characters have become attached to one sex alone, whereas ordinary specific characters have become attached to both sexes; but our theory looks at all the species of the same genus as the descendants of a common parent, with as much certainty as it does at the males & females of the same species. Hence it is not surprising that naturalists have so often described the sexes of the same species, as distinct species & even as distinct genera.—

Ignorant as we are on the primary causes of variation, yet as far as we can obscurely see, the laws governing variation

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are the same as those concerned in the production of species. Therefore, I conclude that the facts given in this chapter, as far as they can be trusted, support our theory that Varieties & Species have had a like origin;—& not that the one Varieties are due to the laws impressed on nature & Species to the direct interposition of the Creator.—