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Chapter 5.

The Struggle for existence, as bearing

 On Natural Selection

In treating of the variation of our domestic productions it was shown that the changed conditions of their existence had some direct effect on them, as food on size, heat on their hair &c, but that indirectly the effect was more important potent in renderingtending to render their whole organisation plastic, or less true to the parental type. This view of the organisation being thus thus rendered plastic in various ways, as if, though of course not really, by mere chance, is, I think strongly supported by the many facts given in our third chapter, showing how sensitive the reproductive functions generally are apt to ha to changed conditions. It was further shown in the two first chapter, that Selection by man, whether intentional or unintentional, combined with the strong principle of inheritance, played a most important part in adding

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But mere fluctuating variability, or any directeffect of external conditions (to which subject we shall return) are wholly inadequate to explain the infinitude of exquisitely correlated structures, which we see on all sides of us. Look at the Anteater with its great claws & wonderful tongue; or at the Woodpecker, or the Hawk which may swoop down on it, or at the wood-boring beetle on which it preys, or at what we consider the humblest creature, the parasite so admirably formed to cling to the its feathers.

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up very slight variations in a given direction.

In the last chapter we have seen that in all organisms in a state of nature there are at least individual differences, & in many some a considerable amount of variation. It would be strange, as before remarked, if this in as much as variability in main part is due to changed conditions, if this were not so, as Geology consists of the history of the long series the many changes which the earth & its inhabitants & its inhabitants have undergone.

 

& from these changes its inhabitants must suffer or profit. No one who has studied Lyell's Principles of Geology will dispute this. Look to our last epoch, within which the far greater proportion of the now living beings have existed, & reflect on the great changes of level the the land of over how a vast an expanse of land in Europe & theboth Americas the sea flowed & left its shells & boulders: reflect on the prodigious changes of climate evidenced by the long intercalated glacial period:

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all those organisms which were so situated that they could not emigrate must have suffered almost every possible change which their organization could withstand; indeed far more, & there must have been much local extinction. Occasionally a living being must get into an island or other isolated site, where it would be exposed to new conditions & yet might survive, like the very many productions naturalised by man's intervention. Some reasons were given in the first chapter for supposing that abundant food might be one main cause of variation under domestication; & it I think I shall be able to show hereafter that the most vigorous species, which are now most vigorous, ranging furthest & abounding most in individuals are those which vary most; & thus we may believe are the best nurtured.

Let the cause be what it may, organisms

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in a state of nature are in some degree variable;

[The paragraph below Stauffer assigned to his appendix: p. 568]

& no doubt external conditions produce some direct effect on them, to which subject we shall have briefly to return; but mere fluctuating variability or the direct effects of external conditions are wholly inadequate to explain the infinitude of beautifully exquisitely correlated structures which we see on all sides of us. Look at the woodpecker, or nut-hatch anteater with its long tongue & great claws; or the giraffe with its long tongue & long neck & high fore quarters—or look at what we are pleased to consider as the humblest parasite & see how beautifully its limbs are formed to cling to the hairs or feathers of the animal on which it lives.

There are insects with admirably adapted structures formed to lay their eggs in the bodies of other insects species of insects, & others are adapted to lay their eggs on special plants, together with a poison, which no chemist can understand or imitate, which will cause the tissues of the special plant

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in question to develop a gall or abnormal growth of fixed form. So The most credulous believer in the "fortuitous concourse of atoms" will surely be baffled when he thinks of those many innumerable & complicated yet admirable manifest correlations which exist throughout the living world. In pure simple cases, as in seeds furnished with hooks so as to be transported by animals, the believers in such a doctrine might, perhaps, adduce the case of the cultivated Teazle, believed by most many botanists to be a mere variety, & yet admirably so well adapted, that it cannot be imitated by man's art, for a special purpose; & he might say as chance in this instance has favoured man, so in another other cases it might favour the plant. But no one I should think could extend this doctrine of chance to every part of the whole structure of an animal, as of the showing in which there is the clearest relation of part to part, & at the same time to other wholly distinct beings. It is superfluous to give examples: any every animal if we know it well, could suffice; but the

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instances are more obvious in some cases than in in others, as perhaps in those given, or as in those insects, which have their structures specially adapted to lay their eggs in the larvæ of other particular species of insects; & others again being adapted to lay their eggs in special plants together with a marvellous poison, which no chemist can understand or imitate, which will cause the tissues of the special plant in question to develop a gall or abnormal growth of fixed form, serving as food & protection to the insect, & appearing like a prison, the dose of which when but out of which the prisoner in due time will knows full well how to escape.

No theory of the derivation of a species or groups of species from a common parent can be thought satisfactory until thes it can be shown how these wondrous correlations of structure can arise. I believe such

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means do exist in nature, analogous, to but incomparably superior, to those by which man selects & adds up a trifling changes, & thus brings his pigeon or canary-bird or flower up to a preconceived standard;—or gets one breed of dog to point to his game & another to retrieve it, in a manner which no wild animal would never follow;—or gets the wool of one breed of sheep to be good for blankets, & another finer & more curled for broad cloth.

If there existed in nature any means by which that man in many slight derivative of variability If those varia slight variations of structure, which we see does exist in beings in a state of nature, occurring in beings in a state of nature & which from our ignorance we attribute to chance, or changed conditions, if these could be selected & added up, not for man's good, but for that of the being in question, in such case the structure of one part in relation might be adapted to another part, or in relation to some a distinct organism being, could be

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at least in some degree & the whole being might be harmoniously modified.

And for myself I am fully convinced that there does exist, always in action in Nature, means of Selection, of which the always in action & of which the perfection cannot be exaggerated. I refer to that severe, though not continuous struggle for existence, to which as we shall immediately see all organic beings are subjected, & which would give to any any individual with the slightest variation of use service to it at any period of its life a better chance of surviving, & which would almost ensure the destruction of an to any individual varying in the slightest degree in an opposite direction. I can see no limit to the perfection of this means of Selection; & I will now discuss this t subject,—the most important of all to our work. This present Chapter will be devoted to the Struggle for existence.

[The last sentence is written over erased? Text in pencil]

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Th The Struggle for existence. All nature, as the elder Decandolle has declared with respect to plants, is at war. When one views the contented face of a bright landscape or a

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[Stauffer assigned these lines to his appendix: p. 569]

was of nature

Struggle of nature. The elder Decandolle in an eloquent passage declared that all nature plant is at war. [pencil insertion:] by not moving [3 words illeg]

 

When one views on a spring day the contented face of nature, or a fine appearance a landscape tropical forest glowing with life, one may well doubt this; & at most such periods not all living things nearly most of the inhabitants are probably contented & happy living with no danger imminent great danger hanging over them & often with a superabundance of food. Nevertheless the doctrine that all nature is at war is most true. The struggle generally very often falls on the eggs & seeds, or on the seedlings, larva & young; but fall it must sometime in the life of each individual, or more commonly on every few at intervals on successive generations & then with extreme severity. This struggle & destruction follows inevitably in accordance with the law of increase so philosophically enunciated by Malthus.*

In a country undergoing no great change, on a long average the numbers of individuals each all the species cannot increase; & unlike man, the lower production other organisms

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* Essay on the Principle of Population 1826. Franklin & many others have clearly seen & exemplified the great tendency to increase in all the lower animals & plants.

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cannot artificially increase their means of support, which must determine the extreme limit of their numbers. Yet all living beings, if not destroyed, even the slowest breeders, tend to increase in geometrical proportion, & often at an enormous ratio.

Everyone must have seen statements of the number of eggs & seeds produced by many of the lower animals & plants.* To illustrate geometrical progression one meets in works on arithmetic states calculations such as, that a Herring in eight generations, each fish laying 2000 eggs, would cover with like a sheet the whole globe, land & water: Linnæus in the Amoenitates Acad. says that an annual plant producing a single flower with only two seeds (& no plant nearly infertile so barren a plant does not exists) in twenty years would yield one million plants. Buffon ranks fifteen animals as less fertile The great-engineer Vauban calculates that from one sow

Buffon ranks fifteen animals as less fertile than man (a statement which I rather doubt); &

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* p. 10

I will copy out a few instances of numbers of eggs & seed: Mr. Harmer in Phil. Transact. 1767, p. 280, weighed the whole & portions of roe & counted in this portion the number of eggs. The number differed considerably in different individuals.

Carp 203.109 and at least 101,200 in lowest number

Cod 3,681,760

Flounder, 1,357,400 and 133,407 do (N.B. These observations on the F. Water fish are confirmed by independent calculations by C. F. Lund in Acts of Swedish Academy Vol. 4.)

Herring 36,960 and 21,285 do

Smelt 38,278 and 14,411 do

Lobster 21,699 — 7,227 do

Prawn 3,806 3,479 do

Shrimp 6,807 4,090 do

Astacus gammarus 12,440 L. Brand Amœn Acad. p. 343

Holothuria 5000 ova in one night Sir J. Dalyell

Doris, 600,000— counted by myself. Journal of Researches p. 201.

Bombyx mori 500. Silliman's Journal. vol. 18, p. 282.

Wasp the Rev. Prof. Henslow counted 300 females in one nest in Autumn

Ascaris lumbricoides, sixty-four million. Carpenter Comp. Phys. p. 590.

This is the greatest number, I recollect to have seen; & it is almost inconceivable.—

Plants

Helenium 3000 seeds

Zea mays 2000

Papaver 3200

Nicotiana 4300} Linnaeus  in Brands Amœn. Acad. vol. 2 p. 409

Wild carrot, (a very fine one) according to my calculations had 40,000 seeds

Wild Parsnip --- according to Rev. Prof. Henslow had 2250 seeds one which I gathered, had I fully believe 12,000 seeds.

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yet man in the United States, has doubled in 25 years. The Elephant is supposed to be the slowest breeder of all living creatures; & I have seen it stated that were this not so, the elephants would overrun the world! The elephant is supposed not to breed till 20 perhaps 30 years old; its length of life is not known, but as one of unknown age when taken lived according to Dr. Falconer 120 years, I think it will not be an exaggerated statement to take 80 90 years as the possible duration of life & that each pair produces four three pair of young: in this case from the both of one first theone pair there is will be at the end of 500 years 5,111,514 elephants alive: or if we assume that in a province the pair produced eight young were 200 pairs these will be nearly at the end of the same period. now are there would be above fifteen millions alive. Hence we can plainly see that it is not from want of fertility that this animal, the least fertile of any, does not overrun the world.

But we have far better evidence than mere calculations of the possible increase, namely the actual increase at a marvellous rate of many animals & plants under favourable circumstances.

The marvellous increase of several of our domestic animals where run wild in different parts

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of America have repeatedly been quoted: (a) Nothing has astonished me so much in this respect as to find in Sarmiento's voyage that in only 43 years after the horse was first imported* (In 1537, see Rengger, Natur. der Sägethiere von Paraguay S. 334.) [1] & run wild

into Buenos Ayres, where it immediately ran wild, it was in possession of the Indians at the Straits of Magellan, 1200 miles to the south. We have similar facts in New S. Wales: thus in 1788* (Report given in Sydney Smith's Works, vol. I, p. 324.) p. 5 29 sheep & 5 cattle were introduced; & 29 years afterwards the numbers were for sheep, 170,920, & for cattle 44,753; & no doubt many must have been slaughtered in the interval. In 1418 a single female rabbit was turned out in* the island of Porto Santo (*by J. G. Zarco in Kerr's Collect, of Voyages. vol. 2, p. 177.) in a few years 3000 were killed at one time; & 36 years afterwards Cada Mosto in his voyage

[1. In Darwin's copy of the book, he scored "& in 1580 (ie 43 years afterwards) Sarmiento saw horses with the Indian in the St of Magellan."]

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(a) for instance the great herds, some even of 8000, seen in Cuba only 27 years after the discovery of that island. (Lyell's Principles of Geology 9th Edit p. 685)

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Robertson quotes for increase of cattle in S. America

Oviedo, ap. Ramusio III, 101 Hackluyt III/ 466 & 511 Churchill Collect III/47 & V/ 680, 692 Feuille, 1/249 Acosta, Lib III c. 33 (8)

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speaks of them as innumerable; Innumerable I should nor is this wonderful ani as it has been calculated (Fothergill Philos. of Nat. Hist. p. 137) that one pair might produce 1,274,840 individuals in four years.

Equally striking & well known are the many facts, showing the astonishing increase of many at native animals, when two or three favourable seasons for any particular animal have followed each other consecutively: thus during the famous drought of 1826-28 (inclusive) in La Plata the whole country literally swarmed with mice, which disappeared with the returning wet. In Germany a similar increase of field mice was accompanied by an astonishing increase in stoats &c which preyed on them. It would be superfluous to give instances the cases amongst my notes of the enormous increase of Birds, fish, frogs, snails & insects, when turned out in new countries: the one island of Mauritius*(a) would afford striking instances in all these classes except fishes; & even in the miserable little coral islets of the Chagos group &for fish we may turn to N. America. Bees & wasps taken from Mauritius have come to swarm, as I am informed by Capt. Moresby on the miserable

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* Sonnerat's voyage aux Indes vol. 2. p. 83. I could add other instances.

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coral islet Chagos islets.

Of the rapid & often overwhelming increase of plants run wild, innumerable instances could be given. America over large districts has been peopled by plants from the old World & in La Plata to a quite overwhelming extent: on the other hand there is scarce a region of the old world which has not got now widely extended colonists from America since the time of Columbus: in India, as I am informed by Dr. Falconer, three of the commonest plants from Cape Comorin to the Himalaya to the are of American origin. In the island of P. Santo.

St Helena

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In the foregoing cases, & innumerable others could have been added, we cannot account, at least in any sensible great degree, for this wonderful, observed rate of increase, by the law of fertility having been suddenly altered in each species. In the higher animals, the period of gestation & suckling, the number of young produced at a birth, the length of natural life, would almost certainly remain constant; probably perhaps probably perhaps the animals might breed would breed at a little younger age rather & oftener du when better well fed than in their native country; but this could not hardly apply in all cases as in short-lived animals & annuals. No one will maintain that the American Parkinsonia has over spread over all India, or that the European cardoon & thistle have overwhelmed the plains of La Plata, owing to their producing more seed than in their sometimes native homes aboriginal land. Undoubtedly the great increase must almost exclusively be due to all, or nearly of nearly all the young surviving & breeding, with the old likewise still surviving & breeding. One should never forget The result of geometrical progressions invariably strikes one with surprise. The observed rate

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& the cessation of increase.

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Nor is it probable that the cessation of increase or actual decrease as mi with the mice of La Plata, would be in any high degree influenced by lessened fertility; for I think the young would perish, before the old were starved to the degree as not to breed; & in the case of the domestic animals run wild they would hardly spread into districts, already peopled stocked with native animals, so unfavourable to render them in any marked degree sterile. Indeed according to Mr. Doubleday's theory, in which for reasons given in our third chapter, I do not believe, but

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of increase in the foregoing instances could not possibly be continued for centuries, for neither the earth nor ocean could hold the product:

& we have seen in La Plata that after four years when the drought rainy weather returned to the incalculable swarm of mice disappeared. No one, I presume will say, that the decrease in these cases was or would be, caused by lessened fertility in the mature animals; for I think it may safely be asserted that the young would perish before the old were starved to such an extent as not to breed. Indeed according to a theory, which has found several advocates, but which seem to me baseless, the fertility organic beings where pressed for food, breed thus more freely, causing the struggle for life to be more fearful.

In a state of nature, all plants annually produce seed, excepting a few which propagate at a great rate by suckers &c, & still fewer which are just able to live on the utmost limits of life in the extreme arctic regions & on high mountains, & where they have to struggle not against other living beings but against cold. All or nearly all animals pair in a state of nature excepting apparently a few males, apparently often in excess, & a few barren individuals. pair Had this not been so, it could

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hardly fail to have been observed in our game-birds & other carefully observed wild animals.*

The time of pairing, I believe, always falls at a period when the animal is at full vigour; though no doubt it is of still more consequence that the young should be produced at a time when food is superabundant & the other conditions of life favourable: hence there is an inherent it is in itself highly probable that nearly all animals pair annually or biennially according to the period of gestation. We have seen how great has been the actual increase of horses & cattle, in short periods, though many must have been slaughtered or killed by accidents; & these animals, when compared to the great mass of living beings must be considered as extremely slow breeders: we know the actual increase rate of doubling of man, a still slower breeder; & we have seen the possible increase of the supposed slowest breeder, the elephant, if allowed to live & breed at its natural rate, even for a few centuries, whereas we have to consider hundreds of thousands of years. Therefore I consider nothing can be

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* note p 17)

With respect to th barren birds, which are not at least in the case of Solan Geese, young individuals, sea f it seems that they are not very rare in sea-fowl. see Wilson's Voyage round Scotland vol. 2, p. 77. For the excess of males see the fact given in regard to Partridge by White of Selbourne in Letter XXIX. But there are other facts mentioned in the same letter in regard to both males & females of sparrows & owls, quickly getting a new mate, when one has been shot, which are of difficult explanation. This fact has been particularly observed in the case of the Magpie: Jenner (in Philosoph. Transact. vol. 1824. p. 21) relates the case of a pair of Magpies with a nest, of which seven were successively shot, but the widow or widower was again immediately paired: in another case given by Macgillvray (British Birds, vol. I, p. 571) six males females were successively shot on the same nest of eggs. One As many nests, especially conspicuous nests like that of the magpie, are annually taken, one may conjecture, that a bird having a nest, offers an irresistible attraction to either sex of a nestless pair, to break their marriage vow.

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more certain, than that every single organic being species on the face of this earth would rapidly increase swarm to an incalculable degree, if many individuals were not continually destroyed at some period of their lives from the egg or seed upwards, either in every during each generation or at every every few at inter short intervals in the successive generations. As

Checks to increase in animals. What are the checks to this possible, & as we sometimes see the actual tendency to a high rate of increase in every living thing?

This is a most difficult & curious question, which cannot be completely answered in any single instance. This subject of the Police or economy of nature has been level ably discussed by many authors from the time of Wilcke in    to the nearly a century ago to the present day when it has been ably handled by Sir Charles Lyell. A volume would be required to treat the subject properly, & I can give here only a few of the leading facts, which have most struck me. The checks are often of a very unexpected nature. Let us look first at th our domestic animals

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become feral in America, about which we might expect to know most. Though both cattle & horses multiplied greatly in La Plata when left on the desertion of the colony in 1537 absolutely to themselves in La Plata, when left in 1537 by the, to themselves, & though subjected to the attacks of Indians; yet at no time have they run wild in Paraguay; & both Azara & Rengger (Naturgesch. der Säugethiere p. 335, & 360)  clearly show that this is owing to the greater number of a certain fly, there, which lays its eggs in the navel of the newly born young. In parts of Brazil, cattle can hardly be kept even in a domestic state, whole herds perishing from exhaustion in the dry season from the multitude of ticks (Ixodes) with which they are infested: (Gardner's Travels in Brazil p. 295, 388): in another part an owner they failed in keeping his stock,from the attacks of blood-sucking bats on the calves.* In La Plata, where these causes do not come into play, great droughts are almost periodical, & horses & cattle of all kinds perish actually by the million, more especially by rushing by thousands into the great rivers, & from drinking saline water. (, Darwin Journal of Researches p. 134). further south we have no droughts, & These droughts destroy multitudes myriads of wild

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*In parts of Demerara Fowls cannot be kept from the same cause, Waterton's Wanderings p. 163, 4th Edit.

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animals, & even birds, whereas we have seen that into this very times during these very same periods mice swarm by myriads to an incalculable degree.—I may add that everyone has heard of the terrible destruction of sheep in Australia from the droughts: so it is in India, & Dr. Falconer tells me in places where formerly one man could kill 30 or 40 Deer could be killed in a day, for some years after a great famine & drought, hardly a single deer could be got. But to return to the cattle, further south in the Falkland Islands, there are no droughts, or injurious flies, or ticks or bats, & the cattle are magnificent animals & have multiplied greatly; but, as I am informed by Capt. Sulivan, who has kept cattle there in these islands, every few years a hard winter like the 1849 destroys numbers, & even those that survive in the following spring are so much weakened that many die of diseases & get lost in the bogs.—The Horses there do not suffer so much from the snow, as their instinct teaches them to scarpe scrape the ground with their hoofs; but they deteriorate in size oddly enough they have multiplied

see Back

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[abstract in the hand of Emma Darwin:]

Silliman's Jour. v. 20, p. 177. In the year 1823 in Livonia in over there were destroyed by the wolves 1800 horses, 1800 cattle, 15,000 sheep, 2500 goats, 4000 pigs, 1200 fowls, 673 geese &c &c.

Rev Encyclop. Sept. 1830.

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far less than the cattle, & here were left to eastern end of the island; though the western is the more fertile (Journal of Researches p. 191): the Gauchos can account for this only from the stallions constantly roaming from place to place & compelling by kicks & bites the mares to desert their young: Capt. Sulivan can so far corroborate this statement that he has several times found young foals dead, whereas he has never found a dead calf. Horses here deteriorate in size, & they are apt to grow lame from the boggy soil, so climate here, no doubt, aids in checking their increase*; & it can hardly but the fact of their increa not spreading seems to show that the check falls chiefly on the young. I may add that Rabbits, though very numerous in certain parts of the Falklands likewise have not spread: what the check is here, I have no idea; or what the check is in Jamaica (Gosse's Sojourn p. 441) where the Rabbit is feral but has not multiplied.

(There can be no doubt that carnivorous animals keep down the numbers of the animals on which they prey. It is worth noticing the number of our domestic animals destroyed in single Kingdom.

The number destroyed, however, must often depend on complex relations: to give a single instance, according to Nillsson (Lloyd Field Sports of N. Europe Vol. I, p. 395) wolves have of late increased in Halland & foxes decreased; & this it is believed

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* It is possible that in this case the Horses' fertility may be somewhat lessened: for in the Shetland Isld (Fleming Philosophy of Zoology. vol. 2. p. 10) the Pony does not reach maturity till its twelfth four year, is not vigorous beyond its twelfth; & breeds only biennially. The dampness of the climate probably is the deteriorating agency, for Wrangell (Expedition to the Polar Sea p. 28) states that in the extreme climate of N. E. Siberia, the Horse is serviceable even at 30 years old.

With respect to the wild stallions killing their foals, the same thing has been observed in Australia, see Haygarth Bush Life, p. 76.

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is chiefly owing to the wolves running down & devouring the foxes, as has often been witnessed; but they can do this only on open plains, so that the proportional increase & decrease of wolves & foxes here depends indirectly on the presence of trees.(a) We are perhaps apt to lay too much stress on the amount of food as determining the numbers of any species; but for it seems for well ascertained that the increase of game in any district, more even in this our highly cultivated country, where so few hawks or carnivorous animals are seen, depends depends depends can more certainly be increased by on the trapping of vermin than any other means.—But there are some few animals which are probably never, either whilst young or old, destroyed by beasts of prey as the elephant; & yet they cannot certainly do not increase to the extent, which their degree of fertility would soon permit: in this case the check is no doubt periodical famines & droughts which we have seen recover occasionally occur in India; & when weakened they would be very apt to perish in morasses, as seems to have happened with the fossil mastodons of N. America. On the coast coast of Africa, Capt. Owen (Surveying voyage vol. 2. p 274) gives a curious account of the sufferings of the

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(a) A beast of prey must often prevent other animals from haunting districts in which they could live and might prefer. One animal

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elephants, which in a body fairly took possession of a town one for the sake of the water & drove out the inhabitants to th who numbered,, it is said about three thousand!

I will give a few other instances of checks to increase from apparently trivial causes. The ferret cannot be kept in W. Indies (Gosse's Sojourn p. 447.) owing to the chigo or sort of flea, which burrows in their feet. In     the half wild dogs invade each other's districts when pressed for food, fight fight & wound each other flies lay their eggs in the slight wounds & cause their death. Everyone has heard how Rein-deer (Wrangell's Travels p. 48) are forced to migrate in vast multitude bodies & annually perish in multitudes owing to the mosquitoes. Dean Herbert seems often to have been perplexed (     ) why certain animals do not increase: he instances the toad, of which such myriads are often seen, showing that they do not perish in the egg-state, & as no animal preys on the toad, he asks why they do not increase infinitely: I can adduce one check, namely a fly maggot of some fly, which breeds in their nostrils, & which destroys thousands in Surrey, as I have seen, & in parts of Kent, as I have been informed by Mr. Brent. But the Dean might have asked with still more force

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why the natter-jack, (Bufo rubeta), which lays eggs enough to people the earth in a few generations, is confined to a few spots in England, where, however, it is common as on Gamling-gay Heath. What animals can seem less concerned with each robbed together other than a cat & Humble-Bee; yet Mr.      shows (     ) that field mice are the greatest most powerful enemies to the Bee, & the cats determine the number of mice, as everyone knows in his house, & hence he believes that Humble-bees are apt to abound near villages, owing to the destruction of the mice. From the facts given in our third chapter, I cannot doubt that the number of seed produced by certain flowers will be determined by the part which Bees play in their fertilisation; & on the number of seed to a certain extent depends the number of the plants; & on them the number of certain other insects & on them certain birds ad infinitum. To attempt to follow the chain of cause & effect mutual action & reaction in any one case, would be as hopeless as to throw up a handful of sawdust feathers on a gusty day & attempt to predict, where each particle of sawdust would fall.

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This subject is so important for us, that I must be excused for making a few more remarks. Our British Birds are probably the best known wild animals. Take the case of the familiar Hedge sparrow (Accentor modularis), which that acute observer, Mr. Waterton, (Essays on Nat. Hist. 2d series p. 95) says will not increase in numbers, however carefully protected. If not killed it could probably live at least seven years:* it generally has two broods of about five eggs, but let us suppose that only every other pair rears any young, & that of each of these only two pair we will say only two pair: this seems we thus seem to allow a fair amount of destruction at an early age; yet if we suppose no that near in Mr. Waterton's house garden grounds there were at one time three were eight pair, the above rate of increase would yield at the end of the seven years,* when the 16 eight old Bird pair would die, 2048 Birds birds; but we have just seen, that though carefully protected by man they do not increase at all. It cannot in this case be any difficulty in finding a place for a nest; & I shd think hardly more than three out of four nests would be taken by cats; & only one out of four nests are supposed to be preserved

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* In the N. American Journal of Science vol. 30, p. 81. It is said that the same pair of Saxicola sialis built its nest in one place for 10 successive years;—a Muscicapa fusca for 9 years; a Turdus for a longer period; Falco borealis for 12 winters. Eckmarck Amœn. Acad. noted the same lawn starling for 8 years; a Motacilla & Kestrel for 6 years.

In Montagu's Ornith. Diet. it is said that a Goldfinch lived in confinement for 23 years.

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in the above calculation. That in many other cases the loss of the nest is a most important check we may infer from the wonderful increase of Magpies & some other comparatively rare birds in Mr. Watertons park, (Essays p. 269) where in one year 34 pair of Magpies bred & reared 238 young ones. The Hedge sparrow in a garden near a house can hardly suffer much from Hawks & the smaller carn wild carnivores, which are so influential in checking the increase of game-birds. I doubt whether the young birds, during the first few months suffer greatly; at least with the Robin everyone must have noticed their numbers in their mottled plumage.

 

& in our migratory birds, as White long ago observed in his letters, the check must fall on the young birds which leave us, for what we imagine to be a more favourable climate, for comparatively few of those which migrate return to us.

The domestic cat is I believe a potent enemy, which with several other occasional causes of death must prevent any great increase in numbers; but I believe nearly all our Birds do go on increasing

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in numbers, till there comes a severe winter,*(a) which greatly reduces their numbers & sometimes exterminates them in certain districts. (Journal of a Naturalist, p. 182) after the winter of 1854,*a judging from the number of nests in my shrubberies & from the number of birds on my lawn, I estimated the decrease at 4 four-fifths compared with previous years. In the summer of 1855, butterflies & moths abounded in an extraordinary manner, which some entomologist naturalists at the Entomological Society attributed, I believe rightly, to the lessened destruction of the caterpillars by birds: the little Tomtit (Parus coeruleus) has been observed to feed its young with caterpillars 475 times in the day.*B With man we consider an epidemic which destroys ten percent as frightful; but what in this above case with the birds it seemed to me that the destruction had been at least 80 per cent.

With the higher animals, as soon as the young can provide for themselves they are generally driven away by the old: in their forced wanderings many probably perish; but some no doubt find a home, especially after any extraordinary period of destruction, in spots where the destruction has been above the average, more especially after any unusually fatal period. Hence it has been observed. The Rev. L. Jenyns informs me that in his Parish Swaffham, during 20 twenty years, very many sparrows

[27v]

*B Macgillvray's British Birds vol. 2, p. 438.

* (a) Severe winters destroy not only the inhabitants of the land, but of the sea; both these certain species on the coast, as described by Hugh Miller (Royal Physical Soc. of Edinburgh Feb 28th 1855), but likewise in on banks under the water: thus in 1820-30 Kroyer (Eding New Phil. Journal 1840 p. 25) says eight million oysters were computed to have been destroyed by the frost.

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& Rooks were annually unmercifully killed for a reward offered per head, but the most careful observer could observe no diminution in their numbers during this period: no doubt the spare birds from the surrounding parishes flocked in; but what would have become of these birds had not there been room made for them in Swaffham? undoubtedly they would have somehow wandered away*, some few have found a home & the others have perished either during the first severe winter year. In all cases, probably, the destruction is unequal in different parts of the region whole total area inhabited by the species; but this does not alter the total final result; for everywhere the rate of increase nor is it applicable to the endemic species of small insulated regions: we may go in imagination from spot to spot, & everywhere the rate of increase is far higher than what can possibly be supported & we may fancy that here & there the conditions of life are so favourable that all survive to their full term of life; but if this be so the destruction must be very heavy in other spots, for, as reprod repeatedly remarked the rate of increase in every living being is so high that the earth could not hold the product. In animals capable of much locomotion, & inhabiting a continent or the ocean, it is likely that many wander to the

[28v]

(note to next page)

* Wilson says in his Wilson's Voyage round Scotland Vol. I p. 368 that in 1833 a pair of sparrows hatched their young in the island of Colinsay, on the West coast of one of the Hebrides Scotland, but that in 1841, he could see no descendants. I may add that Partridge hens have been turned out here but they cau became extinct. In 1841 Rooks bred for the first time in this island. Will they hold their own?

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extreme confines of their natural range & there perish in larger numbers than elsewhere. But how rarely could this be ascertained! (a) Richardson (Fauna Boreali-American p. 88, 263) speaking of the extreme northern range of the N. American Antelope, says that almost every year a small herd lingers on a piece of rising ground not far from their extreme northern range Carlton-house; but few or none "survive until the spring, as they are persecuted by the wolves, during the whole winter." So again with Arctic Fox, he says "most of those which travel far southward are destroyed by rapacious animals; & the few which survive to the spring, breed in their new quarters, instead of returning to the north. The colonies they found, are, however, soon extirpated by their numerous enemies."—

In those animals which produce an astonishing number of eggs, as Fish, the destruction probably chiefly falls on the eggs, as is known to be the case with Fish, from other fish, water-beetles &c. But when the old can protect their young few are generally produced as with the larger carnivorous birds: the Lion, however, produces several young at a birth, but when the

[29v]

(a) text

A pair of sparrows bred for the first time in 1833 in island of Colinsay, one of the Hebrides, but in 1841, no descendants could be seen.* see note back of previous page.

[30a]

(Ch. 5. Checks)

it destroys or injures it to a certain degree; & here more strictly there may be said to be a struggle. between them.

Again another idea comes into play, for it may be said to be chance, which seeds in the capsule of any one plant shall be devoured by a bird or insect, but it may metaphorically be called a struggle which individual plant of the species shall produce most seed, & so have the best chance of leaving descendants;

[30b]  

Carnivorous animals prowling for their prey in a time of dearth may be truly said to be struggling for existence; so when seeds are sown so thickly that all cannot grow, though they may be said to struggle, though not voluntarily against each other. A multitude of animals are directly dependent on other animals & on plants; & plants on the nature of the station inhabited by them; & here the idea of dependency seems quite distinct from a struggle. But a plant on the edge of a desert is often said to struggle for existence; this struggle consisting in the chance of the a seed alighting in a somewhat damper spot, & then being just able to grow live; so it may metaphorically be said that carrion-beetles struggle for existence, when fewer animals die than usual in the any district. In many cases when an animal depends on another or on a plant

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northern Lioness is hunting for food, it is asserted the hyænas prey on her young. In very many other cases the check falls not on the egg, but on the young: thus Smeathman (Philosoph. Transact. 1781, p. 167) says not one young white ant termite out of a million can survive to form a nest. thinks that "not a pair in many millions" of the Termes or white ant "lays the foundation of a new community," common ants being the chief destroyers. In other cases, of which instances have been given, the very young do not seem especially to suffer: thus White of Selbourne long since remarked in his sixteenth Letter that in our migratory birds a vast number move leave us for those returning yearly, from what we imagine to be a more favourable climate for them, than ever return. "bear no sort of proportion to the birds that retire."

[30c]

As in this chapter I have repeatedly the use the expression of struggle for existence; I may here remark that I use employ it in a very large sense.

 

When seeds are sown much thicker together than they can grow, the seedlings may be said to struggle for life, though not voluntarily. It may be said to be chance which determines particular seeds of a late state them in the capsule of any particular plant species one plant shall be determined by by bird or insect; but it may perhaps metaphysically be called a struggle which plant of individual plant shall produce most seeds & so have best chance of leaving descendants;

[30d]

& again it may be said to be called a struggle whether the seeds the plant or the bird or insect which feeds on its seeds gets the upper hand. A minute parasite which lives on as animal, & is absolutely dependant on an certain animal, cannot hardly be said to struggle with it; yet its numbers will certainly generally be dependant on the vigour of the animal which it will peak; & in the same highly metaphysical sense as before but which it will sometimes injure, & with the increasing vigour of the animal those the weaker parasites will perish; so that here there may be said to be a struggle between parasite, & parasite & the animal; as there likewise will be which parasite or which carrion feeding beetle shall lay

the greater number of millions most eggs & so have the best chance of getting into another animal's body or feeding on its carcass.) (I hardly know any living thing being which is more dependent on others, & which seems less subject to a struggle in the strict sense of the word then the Misseltoe; for it depends on certain trees for its support, on certain insects for fertilisation, & on certain birds for diffusion; yet even here, when the several seed seeds are dropped close together there must be a struggle which shall grow; if many grow on the same tree that will suffer. there may be said to be a struggle which bush plant

(30B

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shall produce most seeds & with most tempting pulp for the thrushes; & lastly there may be said to be a struggle between parasite & tree, for the latter will suffer severely from too too many misseltoes.

In many of these cases, the term used by Sir C. Lyell of "equilibrium in the number of species" is the more correct than struggle but to my mind it expresses far too much quiescence.

Hence I shall use employ the word struggle, which has been used by Herbert & Hooker &c, have used including in this term what some may be called several ideas locked & blended together primarily distinct, but graduating into each other, as the dependency of one organic being on another,—the agency whether organic or inorganic of what may be called, whether chance, as in the dispersal of seeds & eggs, & lastly what may be more strictly called a struggle, whether voluntary as in animals or involuntary as in plants.

[30e]

It To return to our subject, it is difficult to realise that every animal was living by a struggle animal is kept down by a severe sufferance struggle struggle; yet it accords with, & aids us in understanding, much that is passing around us. Lighten the pressure on any one organism in the slightest degree, quite inappreciable by us, & the its elastic numbers will instantly increase. We can perceive why with extended cult. Why are some species rare or quite absent in one district, & abundant in another, under, as far as we can judge, similar

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conditions. Innumerable instances could be given; & several even within the limits of England; as the absence of the night nightingale in Devonshire, water-wagtails (Motacillae) & carrion-crows in certain parts districts: during 15 years I have only twice seen a swift (Cypselus) in the parish in which I live; yet how common a bird over nearly all England. We can perceive why the sparrow & partridge have increased in numbers in some districts with extended cultivation; but who can explain why during the last 20-30 years the Missel-thrush (Turdus      ) has increased* near in Ireland, Scotland in England, as I have likewise myself noticed. Why did has has did the Robin (Sylvia rubecula) decreased decrease & finally disappear in the year in parts of Belgium. A small wading bird (Pelidna    ) has increased of late considerably on the shores of the United States.

In New S. Wales as Mr. Sutton stated before the Geographical Society some parrots have greatly decreased, & some disappeared; others equally conspicuous as the white cockatoo have remained in about the same numbers, & others as the Blue Mountain parrot have increased. No doubt if we go had accurate accounts we form in past centuries, we shd have endless cases of great changes

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in proportional numbers: I will give only a single instance from Prof. Nilsson.* a large Bat (Vespertilio noctula) is now common in Sweden, having appeared about the year 1825, & was quite unknown to Linnæus; but it seems from the bones found in parts of the walls of the Cathedral, which it now again haunts that about 700 years ago it was also very common. Lastly it is the common rule, that a species is abundant within what has been called its metropolis, & towards the confines of its range both in longitude & latitude becomes, often rather abruptly, rarer & rarer, till it disappears; & there seems to be no difference in this rule, whether or not the beings be locomotive: yet as it can exist towards the confines of its range, & as its fertility certainly usually then lessened, how is this?

In such cases, & in all the foregoing these cases, namely of a species abundant in one district & rare or quite absent in an adjoining one,—in their cases of increase or decrease in numbers,—we shall feel little surprise, if we steadily look at the average number of every single species in its most favoured site, as determined by a severe struggle, of which in no one case d can we ca perceive

[32v]

* Report Brit Assoc. 1847. p. 79. Prof. Nillson gives other curious instances: the water-wagtail, (Motacilla alba) was very numerous 30 years ago, then it vanished & now again has reappeared.

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all the elements: the merest grain in the balance will then determine whether the range should be lessened or increased.

The manner in which the diverse checks act & react must be exceedingly complicated. When there is no compensation there will be a slow steady but slow decrease in numbers: thus when man "the fur-trade even when best managed has always been a decaying trade," & post has to be pushed beyond post into the interior: so it has been with whaling; but how different our game-bird. Neither partridges, or grouse or hares are fed, & yet how many hundred thousands are annually killed with no decrease in the stock: no doubt they could be killed out exterminated as the capercailye has been: in this case there can be no doubt that this is [illeg]with our game man compensates by the destruction of vermin, & he kills most before the day many which would otherwise have perished during the winter. Let not a gun be fired or a trap set in England for the next 20 years, & I think it may safely be predicted that there would be less game, almost certainly not more. For instance

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Bruce remarks (Travels vol 5. P. 84) that in Abyssinia Boars, foxes & Hares are held unclean & are not hunted, but yet they do not increase in numbers; & he accounts for this by the number of Hyænas; a statement as far as Hares are concerned but whether Hyænas shd would destroy many hares may be doubted.

Whatever the average number of a species in any country may be, the average being determined by a complex struggle, that number will steadily decrease, if we add without any compensation the least additional cause of destruction, until the species becomes extinct. But the rate of decrease will be very slow: if we have 1000 individuals & we destroy on an average one ten per cent more every year at the period when the number is least than were heretofore destroyed, it will take 229 298 years to reduce the numbers to one hund fifty. But generally often with the decreasing numbers of the an organism destroyed, the numbers of the destroyer will be diminished, & the check thus lessened & its action almost infinitely prolonged. It may well happen that a large additional number of a species might be destroyed without in the least lessening

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their average numbers; for the destruction may fall before an habitually recurrent period of dearth, which would have in any case thinned their numbers: it is even quite conceivable that such destruction might even increase the minimum average, of the for more food might thus be preserved against the period of dearth, as for instance in dry countries, in which the herbage dries withers up & serves as natural hay. Many other considerations might have been added showing how complex the action & reaction of the checks to increase must be.

Besides the many & complex checks tending to cause a decrease in the numbers of a species; an inordinate increase, under the most favourable conditions, is prevented in some cases at least, as in our game, by the mysterious epidemics, which seem connected in a manner we know not how, with the closer aggregation of many individuals of the same kind.—

The great difficulty, which at least I have experienced in fully realising the struggle goes for life covertly going on around us: I think is partly due to our familiarity with our domestic

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animals. We see how easily they are reared, how long they live & how seldom they perish from accident; & we forget overlook our care of them whilst very young & that we artificially preserve food for them & so prevent recurrent famines; but the millions annually slaughtered over Europe, with the stock still kept up, ought clearly to show us what destruction there must be with the allied animals in a state of nature. Nor ought we to feel the least surprise at our not being able to point, how, when & where the check falls on any animal in a state of nature: for the case of man, in some respect more simple &, incomparably the better best known, (& in some respects more simple, though in others as in the moral restraint check of Malthus or as Laing more correctly calls it the prudential restraint, very much more complicated) shows how ignorant we are.

Without careful statistical tables: how little could we have judged of the different rates of increase, & expectancy of life amongst different ranks, at different times in different countries & even within the limits of the same town.*

[36v]

* Mr Neison shows has shown (Statistical Soc. March 17th 1845) that in the same town the expectancy of life with ma mature men of different trades differs in as much as by 50 per cent.—

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(Ch. 5. Checks) animals & plants)

Mutual Checks of Animals & Plants. We have considered as yet almost exclusively the manner in which animals check the increase of other animals. But plants & animals are even more importantly related in the same way; as are plants with plants.

This subject is so important for us, in several ways, that I must be excused for entering into some details, but they shall be few. All animals live on plants either directly or indirectly; & their breath is the plants' chief food; so that the relation of the two kingdoms on a grand scale is very obvious. But it is probably much more precise than it at first appears. One at first supposes that grass-eating animals devour all plants nearly alike; but of Swedish plants it has been ascertained (Stillingfleet Tracts. 1762. p. 361, on authority of Hassellgren in Amœn. Acad.) that oxen eat 276 kinds & refuse 218; goats eat 449 & refuse 126; swine eat 72 & refuse 271 &c. Southward of La Plata, I was astonished, as others have been, (Journal of Researches p. 118) at the change effected in the appearance of the plains by the depasturing of the cattle; & could not for some time believe but that there must have been a change in the geological nature of the country. What the smaller animals quadrupeds plants the many small

37v

We here considered

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(Ch. 5. Checks —animals & Plants)

rodents live upon is seldom known, but every one must have heard of the destruction of whole plantations by mice, & rabbits &c. I have heard it remarked that all, or nearly all our spinose & prickly plants are liked by the larger quadrupeds; the spines being an evident protection to them; & I have sometimes fancied that the very common prickliness of the bushes on desert on plains districts in place countries, when the vegetation was is scanty, as almost every traveller must have observed was chiefly due to the greater protection from animals requisite for any bush to live, where the vegetation was scanty. It has, also, been shown in detail by Forskahl remarked that those plants which are not eaten by cattle are attacked in an extraordinary degree by insects; from 30 to 50 species sometimes preying on a single plant: I presume a plant preyed on by both insects & quadrupeds would be exterminated.

I will not do more than allude to the enormous amount of injury, even to extermination, effected by insects on plants; on which subject copious details are given by Kirby & Spence.5 Land mollusca are, likewise, potent enemies to many plants, especially when young, as every gardener knows: and in one cas early on a dewey

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(Ch. 5. Checks —animals & Plants)

morning in what extraordinary numbers they sometimes swarm! In all these cases the relation is obviously mutual: the increase or decrease from any cause of plant & animal mutually affecting each other.

But animals serve plants, as well as destroying them; & in destroying some plants they invariably favour others. In how many ways do they transport their seeds! Though as animals may Even when they devoured the seeds if one out of a thousand escapes escapes, it may be of the utmost importance to the plant; of which I shall presently give a curious instance. Though Bees devour much pollen, They a they are sometimes indispensable to the fertilisation of some plants, & generally most useful: different some plants are visited by one different kinds of Bees; & some by none, but which absolutely require use other insects in order to produce seed. Worms I believe (Geological Transactions vol.    ) I believe play an important part for plants in turning up, over in short the ground, & in burying planting the seeds. In hot weather how cattle collect under the most shady tree I have often thought when seeing the quantities of manure collected under the most shady tree in a field during hot weather that even this in the great war of nature

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might make a sensible difference in the vigour & number spreading of a tree: on the other hand, Lieut. Breton (Tasmanian Journal Vol. 2. 1843 p. 136) says he has known in Tasmania that trees have perished which were flourishing have actually perished as soon as the land was depastured; & he suspects that this is caused by the ground being bared & thus dryed.

At St. Helena the upper plains, to an extent of 2000 acres were originally wood wooded, & it It seems pretty well made out that the goats & swine which were introduced into St Helena (Darwin, Journal of Researches p. 489) in 1502 & soon multiplied, destroyed all the young trees; & that by degrees the old ones perished of age; so that 220 afterwards it is said "the old trees have mostly fallen"; & now the upper plains are al covered with grass without a single tree many of which Some of the trees are known to be now absolutely extinct. In the surface soil, I collected eight kinds of land-shells, now extinct species; & their extermination was indirectly & that of many insects has likewise been in all probability, indirectly due to the goats. To give one more example: near Inverorum in Scotland, I saw a whole hill-side covered with young birch-trees so nearly of the same age, that I enquired why so useless a

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tree had been planted; but was told that about ten years before the district had been here converted from sheep-pasture into a deer forest; & that sheep devour young birch-trees, but that deer do not. The growth of the birch, would certainly greatly alter the vegetation on the whole bank; & with the plants, the insects would change; & with them, the birds, would change of which I shall presently give an gi instance. It is not too strong an expression to say that the introduction of a single mammal might change the whole aspect of a district, even to the minutest living details.

On the struggle between plant & plant: the struggle here is not so obvious, but not less certain. Plant does not actually prey on plant, excepting in a few root & branch parasites. In every most cases  Nearly all plants, however, are favoured by the decay of others; and this is indispensable to those which live in peaty earth. In very many cases, also, shade is indispensable or highly favourable: but in plants growing in the shade of others there is some, though perhaps slight reciprocal action, for such plants must rob their over shadow protectors of some nutriment;

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as we see in the greater vigour of our orchard fruit-trees, when the ground is kept bare beneath them. Plants, also, often offer protection to the seedlings of others; & as Stillingfleet (Tracts p 74) has remarked how often do we see a seedling young tree springing out of a furze or thorn bush on a common which has protected an every it from the attacks of cattle, an enemy which will but ultimately to become cause its over destruction destroyer be overshadowed & destroyed by it.

Generally the struggle between plants is more like that of those quadrupeds in the same country, which devour the sa nearly the same kind of food.

We have evidence of the struggle on a grand scale in the many thousand hardy plants which can be perfectly preserved by simple weeding in our Botanic & common gardens & shrubberies, but which never spread beyond our gardens or spread to perish. (a) text

It is instructive to note keeper of garden refuse in to observe how frequently foreign plants spring up for a year or two in one of rubbish hole of thrown from a garden; but how infallibly certainly in a

[42v]

(a) text Long ago near Montpellier, Gouan was in the habit of sowing all kind near Montpellier many foreign seeds likely to grow, but few several of which succeeded for some years; but Mr. Bentham informs me that he searched in vain, & all are now extinct: the ground here is so sterile & bare, but & we must suppose the native plants in the long run beat the foreigners in the spots where both could grow.

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(Ch. 5. Checks plants)

Few a year, more or less, they are overwhelmed by our native weeds. The foreigners languish, perfect fewer few seeds; & of these seeds, few germinate; & the seedlings seedlings are generally smothered. (a) In our nature uncultivated native banks & woods, I believe many far more seedlings of our native plants rise spring from the ground, than can possibly come to perfection; this may be conspicuously observed with some of our nativ trees. We see the same fact in our agriculture crops; for thin-seeding requires good farming,—that is land with the seeds of many weeds on the land many seeds of the crop wanted must be thickly sown, to give let give the right number a chance of succeeding.

In our gardens we can raise common culinary plants with certainty; but sow the same seeds in any number on an adjoining grass-field, where there would be nearly the same insects &c to animal enemies, & you will not raise a plant. Preoccupation of the ground, no doubt, is most influential against chance seeds; but its power has been, I think, by sometimes overrated: all plants in a state of nature undergo a kind of rotation of crops, exhausting one spot & springing up in another, supplant being supplanted & supplanting others: in a coarse meadow the patches of Dactylis &c. which are not browsed, if marked, will be found to change their place; so that if seed be annually sown

[43v]

(a) Rothof (acts of Swedish academy vol. 4.) sowed 39 kinds of hardy garden & agricultural seeds on a long earth thrown out of a ditch in a bog in process of being reclaimed, & only seven of nine came to maturity; eleven seemed capable of ripening their seed; twelve germinated but did not thrive & nine nine did not germinate.

(whither insert?)

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The seed if a plant fitted to succeed overmaster the others, be annually sown it will at last find a proper site. And the many naturalised plants in every land from the even chance seedlings will sometimes seize on to an gain the day & overwhelm gain the day fix themselves not rarely intrude on a preoccupied surface. Seeing on what a nice balance of power a plant can become naturalised, it is no wonder that the most skilful Botanist though he may very safely say some will not cannot in the least in the least predict, as was remarked to me by Dr. Hooker, what plant can will become though he may safely assert that some will not, become naturalised in a what given country,

No one will question that almo every plant is limited by that there is a limit of heat & cold, dampness & dryness, which beyond which a plant cannot survive; but I think very d it seems that very few plants reach this extreme limit. This may, I think, be inferred from what they can endure in our gardens; but more especially as occasionally once or twice in a century we have an a winter of extreme cold or less hot a very chilly or very dry or wet summer; & yet I have not seen any record of a zone of dead plants having been observed towards this the confines of their natural range. And yet But what a havoc an extraordinary winter will make in our gardens & more especially in our shrubberies!

It may be inferred from this, that owing to the struggle between plant & plant, hardly any species reaches

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(Ch. 5. Checks plants)

very near its extreme climatal limit. In extreme arctic regions & on lofty mountains, where each plant has to struggle against but few other living beings, but against severe conditions; i zones of dead trees have been observed, as by Hearne Ledebour on the Altai, & by Hearne in N. America, who describes a band of dead and blasted tree stumps upwards of 20 miles in which width beyond the living wood. (Ledebour, in Hooker Bot. Miscell. vol. 2, p. 251. Hearne's Journey to the Northern Ocean p. 101)

It seems even very doubtful, whether plants towards their northern & southern ranges limit, become dwarfed are stunted & degenerated, as so very commonly hap may be seen in ascending a mountain. I have not met with any precise observation on this head. ¶

(In the arctic regions & on high mountains very many plants become much stunted; & though I have not met with any precise observations on this head, I think it would infallibly certainly have been noticed had this often happened often with plants at their lower limits on a mountains & at their southern limits in the lowlands: of this latter case I have noticed only one instance,

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(Ch. 5. Checks Plants)

namely the Sugar-maple which in the southern par United States is said (Kalm Travels in N. America Vol. 1, p. 142) not to attain above the third of the height which it has does in Canada: on mountains, also, I have met with only one instance, namely in the Beech, which is stated (     ) to be stunted below the level of — on the       . Again when the northern limit range of a plant does not fall near the Arctic regions, it does not seems to be very seldom to become stunted at its northern conf limit: as several British plants do not range beyond Northumberland & Durham, I applied to asked Mr. Story, who with some friends to attend to this point for me, & he has sent me a list of 32 plants observed in this predicament observed by himself & friends & it appears that only three or four 2 or 3 two or three of these are at all dwarfish. Trees,* (Alph. De Candolle Geograph. Bot. p. 72) however, seem more commonly to suffer I presume, from being more exposed to the winter temperatures: & several of our British trees become dwarf in Scotland; & so it is according to Kalm* with the Sassafras & Tulip-tree in the United States. (*Travels in N. America vol. 1. p. 142.—Sir G. Grey in his Expedition vol. 2, p. 262, says that the Xanthorroea Xanthorroea, though not a tree, declines in health & growth in proceeding northward.)

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(Ch. 5. Checks Plants)

These several facts are explicable if we look at plants as generally not actually limited by climate, but by struggling with other plants under conditions beginning to be unfavourable; for on on the lower limits the limit struggle & consequently to limit would struggle would be severer in proportion to the number of enemies or opposed species, & these would be more numerous at on the lower than on the higher slopes limit of in parts of a mountain, & in the colder temperate regions, at southern than in the northern half of the our colder temperate regions.

No one has written more forcibly on the struggle between plant & plant than the experienced horticulturist, the Dean of Manchester. He Mr. Herbert shows (Journal of Hort. soc. vol. I on the local habitation of Plants vol I. p. 46) most clearly that those plants more especially those living which live in sterile & peculiar soils often do not grow live there on this or that soil, or under this or that degree of moisture, not because they like prefer it, but because they can thus "get a poor livelihood in peace & quiet" and their "enemies cannot grow than than to choke them." Speaking of some Crocuses confined to sterile mount hills in the Ionian islands he says that when secured from their native soil & transported into a garden they acquired ten-fold vigour.

There are many cases on record* besides the striking

(Alph. De Candolle Geograph. Bot. p. 428, 453, 455)

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Ones given by Herbert, of the same species growing in very different situations in different countries,—for as Herbert instances — Herbert the Orchis monorchis & militaris in England on chalk Banks, named by Herbert & in reed-beds on the edge of Lake of the Brienz, (a) such cases are probably in main part though not exclusively due to no other plants more vigorously occupying the sites in one or both both countries which the species in question would most enjoy; for with such a range of so flexible a constitution there would be few sites on which they such plants could not grow or exist.

To show how one plant can influence others, & likewise many animals, I am tempted to give one very common case. In Staffordshire on the estate of a relation, where I had ample means of acquiring all particulars, there was an extensive barren heath, of which never touched by the hand of man; but on one side over several hundred acres had been planted about 25 years before with larch & Scotch-fir, nothing whatever having been done, excepting small holes at the proper [illeg]having been dug, & the whole enclosed. The effect on the native vegetation was quite remarkable in the very great immense change of in the proportional numbers of the Heath Heath plants found all on the Heath; & in the presence of 12 species (not counting glumaceous grasses & carices to which I did not collect attend) not to be found growing

[48v]

(a) text

, or — the common milkwort (Polygala vulgaris) in England on dry upland pastures, in Zante on alluvial & very moist meadows.—

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on the Heath; of these twelve, three had never been found observed elsewhere in the neighbourhood by a relative who had attended collected collected plants attended pretty carefully to the botany of the secondary district. The change in the insects must have been even greater; for six insectivorous birds was were extremely common in the wood & were not to be seen on the sam Heath; where two or three other insectivorous species lived, but did not frequent the plantations. I was interested by one particular: young oaks were springing up of all ages by hundreds, in parts at the distance of a mile from any oak-tree, in such numbers that I here & there a actually appearing as if they had been sown broad-cast; so that I particularly enquired but I was assured that this never had been the case; & the woodmen told me that there was not the least doubt how they came there; that they had repeatedly seen rooks carrying dropping acorns in their flight across the woods: there was no rookery near, & the line of flight would take the birds across the heath where there were no oaks, so that this curious & most efficient means of dispersal must have been wasted for centuries, until the decay of the leaves of the fir-trees & the growth of other plants had made a bed on which the acorns soon after being dropped could germinate. I have given instances

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to show what an effect the introduction of a single quadruped can indirectly produce on the vegetation of a country; & here we see that the single introduction of a tree, with no other change whatever, can produce as great an change influence on other plants, birds & insects.

Make the ground quite bare, as on a railway cutting, & it may be almost said to be chance by what plants it will be at first covered, being dependent on the nature of the soil, the kinds of plants growing near, the means of diffusion & number of their seeds & the direction of the wind; but in a few years, notwithstanding that the number of the seeds of the first occupants will may will probably have been increased a million-fold, the proportions will greatly change, & ultimately become the same as on adjoining & similar old Banks. Many curious accounts have been published of the change of vegetation when a N. American forest has been not burnt or cut-down & then left to nature.

This has been called rotation; & it seems prett certain, that a pretty clear (Alph. De Candolle. Geograph. Bot. p. 448, 472.)

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that in our meadows & woods, when not suddenly destroyed that there is a real rotation of the plant, like that followed by farmers & probably dependent on the same causes, viz chiefly exhaustion of the various chemical elements in the soil required in different proportions by the different families of plants. The same principle probably comes into play in causing the beautiful diversity of plants in our meadows & woods: the good farmer every fifth or seventh year plants the same crop on the same field; but on the nature has sows raises her crops altogether in exact proportion to what the soil can support, & other potent causes each kind slowly changing its place, with this great difference that she is not the determined enemy of any bird, insect or slug, & cares not what or how many which what which plants overmaster the others. But when a forest is burnt down, whilst still in full vigour, & other a very different vegetation, as is invariably the case, springs up, it seems doubtful whether this should be called rotation in the above sense; the change would rather appear to be due to what seeds are ready in the ground, or quickest brought there; on the rate of growth of the seedlings & their immunity from animal attacks. In these cases, in the course of centuries the trees

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reassume in the course of centuries ages the same beautiful variety in the same exact proportions as in the surrounding virgin forest: this has been noted in many parts of the world, as over the ancient American ruins in Central & North America.

(An Enquiry into the Origin of the Antiquities of America by J. Delafield.)

On how many & complex contingencies must this wondrous battle prolonged over centuries have been determined by which each species has recovered its rights!

It is indeed a wonderful conflict, on which I cannot cease marvelling. Causes appearing to us most trifling are potent. In the Staffordshire Heath formerly alluded to, a small portion had been broken up & attempted to be cultivated, for two or three years; but had utterly failed & was thus planted with fir trees at the same time with other parts of the heath; & 25 years afterwards, the undergrowth was so different that the lines of separation could be most easily traced. In walking over the most barren heath where three or four or five plants held absolute sway, I have often been surprised to see [illeg]a line of turf com along small pathways: is this owing to the heath being mechanically destroyed? or do

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animals follow the paths & occasionally, though rarely drop a little manure? Manure may be directly injurious to the species of Heaths; but vege I have noticed in a neglected field of my own, that slight manuring caused a marked decrease in the hard-heads (Centaurea nigra); yet this plant certainly likes manure, but the more vigorous growth of other plants must have checked its increase. In this same field I have observed in different summers, an obvious difference in the proportions of the several plants; showing how rapidly a slight change in season caused allowed one species to increase over another. So again in old meadow land, which has been ploughed years ago, the same species may be observed in the slightly damper furrows & slightly dryer ridges, but in different proportions: in this (& other such cases) there can be no doubt that the plants growing both in the furrows & on the ridges, could for a time cover the field, if all the other plants were exterminated, but that having to struggle with other plants, the slightest difference in dampness, determined the proportional numbers in either case.

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(The old divine Jeremy Taylor says asks  says, "Tell me why this turf this year brings forth a daisy, & the next year a plantane." No one can answer.

But let it not be called chance. The chemist may throw a dozen salts into solution & may hope to predict the result; the naturalist cannot do this with the living beings dispersed by ten thousand ingenious contrivances all round him; but when we see the virgin forest resuming reassuming its beautiful & a variety apparently in the same exact proportions, over the ancient Indian ruins, we must see how little of what we call chance has to do with the final result.

This struggle, this war of nature, becomes only in the least degree intelligible to us, by keeping steadily in mind that each plant & [illeg]would for a period cover the ground for a period if left to its natural powers of increase; for no one will doubt if four-fifths of our British plants were suddenly exterminated, the remaining fifth would almost indirectly soon decently clothe the land. Surface ground.

(a) text Assuredly every single plant, even the most vigorous & predominating in its nature, is habitually destroyed in multitudes at some period of its life from the seed upwards, either annually or at recurrent periods, by means, which we very

[54v]

(a) text

[54vv]

One may wonder why any one or half-dozen of the most vigorous plants in England, annually producing thousands of seeds, & growing in all sorts of ordinary stations, existing here living in the middle of their range & therefore well capable of bearing somewhat more heat & cold, damp & dryness, why such plants do not monopolise the whole surface. But assuredly

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[Slip of paper pasted on:] seldom can perceive; & that the only difference between the strong & weak in number being the weak & strong being that proportionately to the number existing ay any time small is or has been at some time destroyed less than the other is now being destroyed [illeg] strong less than the other. the weak one has been destroyed during former generations or has been prevented increasing, more than the one called strong.

(In considering the facts now given, & many similar ones are known to any naturalist, one caution is perhaps necessary. Although certainly the most different organisms very often act & react on each other in the most complicated way; yet from such cases exciting our surprise we may perhaps be led to attribute too much to this mutual action from remote parts in the polity of nature. That part of the complex idea, which I have employed of for expressed, as before explained by term struggle for existence, which is more correctly expressed by dependency, generally relates to organic beings remote in the scale of nature; & individuals of the same species are never hardly ever dependent on each other, excepting in their sexual, parental & social relationship. But we have seen how dependency graduates into a struggle for existence. On the other hand that part of the idea, more correctly expressed by the word word struggle, applies in its fullest force to between individuals of the same species. When we remember that individuals

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of the same species, whether animals or plant, live on nearly the same food & are exposed to the same dangers & difficulties, it is in itself probable that the struggle will be here most severe at some period of life. It Probably it will be nearly equally severe between the individuals of two varieties, when they meet, & secondly between closely allied species for they usually have nearly related habits, or between species or between organisms, however different in structure, if they have nearly related habits & encounter each other. (a) And lastly the struggle will often be most very severe with the external inorganic & climatal external conditions of existence independently of the coinhabitants of the district.

We have some evidence how powerfully allied species affect each other: every one has heard how the Norway Rat has exterminated the Black Rat under the most different climates & circumstances of all kinds from the Polar circle*(1) to within the Tropics, in the New & Old world: in New Zealand*(2) the Black Rat had previously almost expelled an aboriginal on a previously introduced species: in Färoe*(3) "the decrease of the mouse has been in proportion to the increase of the Rat," so that the common mouse, which was the earlier inhabitant, has almost de is now has been almost exterminated.

[55av]

(a) What can be more remote than a locust & a ruminant quadruped, yet they must often powerfully affect each other. In the cases of rare species, having few individuals thinly scattered, we may infer that the struggle, as far as organic beings are concerned, is chiefly with other distinct species or conditions of existence

* (1) Lloyd Field Sports of N. Europe vol. 2 p. 321.

* (2)

* Landt Description of Faroe p. 213.

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Even with varieties of our domestic animals it has been found by experience (Ferguson,

(The Northmen in Cumberland by R. Ferguson p. 22. 1856) that other breeds of sheep cannot exist on the mountains of Cumberland with the Herdwick breed, "for they stand starving best." If one species of Swallow were to increase we might expect that other Swallows would suffer more than other Birds; & so it seems to be, for with the late curious increase in parts of the United States of the Hirundo fulva, the Barn swallow has decreased. (Dr. Brewer in N. American Journal of Science, vol. 38 p. 392). When the red-legged Partridge increases, the common Partridge decreases; so it has been observed with the Pheasant & black-grouse. So Again Fish of the same with allied habits must chiefly affect fish; & thus the shad (Clupea sapidissima) has increased in the Hudson, few actually in parts full twenty-fold, owing to the erection of a dam, & the consequent decrease chiefly of another species of Clupea. (Mr. Adams in N. American Journal of Science Vol 20. p. 150). In Russia the small Asiatic Cock-roach (Blatta asiatica) has everywhere driven before it the great cock-roach. (Pallas Travels in Russia vol. I. p. 16.)

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The    Leech exterminates the    when placed in the same pond. And to go to the other extreme of the scale how fatally does civilized man cause the extermination of savage men.

I have said that the struggle is often severe with the a between organic beings & their extr conditions of existence, independently of the other co-inhabitants: this chiefly holds good on the confines of life, as in the extreme arctic regions or on the borders of the Sahara a desert like the Sahara. When animals & plants actually perish from cold or drought, there cannot be said to be any struggle between the individuals of the same species also with another; but each between the constitution of each & the destroying element. But more generally, the cold or drought for instance, kills by lessening the food, & then there may be most truly said to be a struggle which between the individuals of the same species or of species with allied habits. shall survive.To give one instance to show how indirectly during such periods one may variety may indirectly master another: in La Plata, during

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the great drought, the cattle perish chiefly from famine & the niata breed would be utterly exterminated, if not protected, for from the peculiar shape of their the jaws they cannot feed when all the dried up herbage has been consumed on twigs of trees so well as the common cattle; can when driven to the last extremity; but if there were no bushes whatever in the country one all the dryed up herbage was not first devoured by the common cattle, the Niata would no doubt succeed pass through the ordeal, for at in all other respects they are a strong & healthy no doubt probably the niata cattle would pass through the ordeal as well as the common cattle breed; both with greatly reduced numbers.

(Hence, I think, we may conclude, that as a general rule, that that the struggle for existence in its strictest yet never simple sense is most severe between the individuals of the same species, & next between the individuals of two distinct varieties, or species, or even classes if their habits are somewhat allied. In all cases, the struggle being ruled & modified by multiform relations.

[pencil insertion:] In all cases observed modified in as way of external condition]

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Facts apparently opposed to there being a severe struggle in all nature:— I will now give the few facts cases which alone have seemed to me to throw doubt on the foregoing conclusions [illeg]struggle for existence. Perhaps the most striking is the existence of species, even locomotive species as mammals, confined, without any physical barrier & with no difference in conditions appreciable by us, to a very small locality, but there very abundant; for it might be argued that if there be such a power of increase, & as the species is abundant in the locality in question, showing that the conditions of its existence are there favourable, why does it not spread.—Many instances in all classes could be given of facts of this nature: Mr. Bentham has often insisted to me, how remarkable it is that certain plants should be found in a single spot, as the Pyrenees & no where else in the world; & should there be abundant; & therefore apparently not like a species on the point of extinction.*a

Some local species have dying out species. The case is the more been known to exist in the same place

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*a Bartram in his Travels (p. 466) speaks of "a singular and unaccountable circumstance" namely that he found a Franklinia (Gardenia) alatamaha growing plentifully over two or three acres in E. Florida, but that he never met with elsewhere. Mr. Wollaston (Variation of Species p. 153) gives plenty of cases of common insects, though extremely local insects, in Madeira.

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remarkable as in some instances for one or two centuries.1 (Al. De Candolle. Geograph. Bot. p. 471) it is historically known that a plant has been numerous in one small site, during several more centuries. But by far the most remarkable fact case of this nature on record, is that of certain species & even varieties of land-shells in Madeira & P. Santo, are positively stated by Mr. Wollaston (On the Variation of Species p. 132. Helix Wollastoni is one of the most striking cases, & the varieties, as so considered by Mr. Wollaston,) of H. polymorpha obey the same law) to swarm on certain hillocks on these islands, where they are also found fossil, & that they occur no where else either fossil or recent in the whole group, which has been thoroughly well investigated. The superficial calcareous beds in which these very local land-shells occur, include a few extinct species, & I am informed by Sir C. Lyell that the island has undergone considerable change since their deposition: hence we must conclude that these land shells, each on its own site, has swarmed probably for several thousand years, & yet have were spread just held their own place & have never spread!

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In considering cases like these latter of the above nature, these same to has not difference between them less difficulty in in which each district has a representative species, filling as far as we can perceive the same place in the economy of nature, the difficulty is, perhaps, not just so great as it at first appears; for let us take the cases of the same identically the same land-shells inhabiting two hills a few miles one of those a common land-shells, apart, I should think that probably that the inhabitants of one those two hillocks were the lineal descendants of the descend first colonists of the two hills, without having in many cases been at all intermingled at all; for although no doubt the checks would fall much heavier at some times than on the inhabitants of the one hillock than on the other; yet if they were not wholly exterminated on the one, the rapid power of increase common to these & almost all the lower animals, together with their slow power of travelling, would allow the survivors of the hillock which had suffered most to breed up their numbers before they could be invaded by the inhabitants of [the] other hillock, though they would be to a certain extent by the inhabitants of the intermediate low land; but during another season the lowlands might be invaded by highlanders. The result would be different with slow breeding animals with high having rapid powers of travelling as with birds, or plants having seeds easily blown by the wind. Thus far I can admit, the importance weight of power

[57v]

which we positively know, from the extraordinary numbers occasionally appearing in favourable seasons, can rapidly increase, & is therefore habitually kept under by checks of some kind; & let us suppose it to inhabit two points hillocks a few miles

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slow diffusive progress, to which Mr. Wollaston* attributes so much importance (Variation of Species p. 125, 130, 153). The result would, also, be very different if the land-shell inhabiting one hillock was a variety having the smallest advantage over the individuals in the intermediate tract & on the other hill, for it then it would surely spread; but in the Madeira case we must may at b suppose that at the very least each distinct long species or variety long inhabiting its own hill is at the very least as well adapted to the conditions (I do not mean mere climatal conditions) there found occurrent as on to the conditions of the other hill. Nor should we forget that we shall presently

(Those cases in which a plant is very abundant is absolutely confined to on one small area, without any apparent reason, & found no where else in the world & is very abundant, without close representative species in other adjoining districts, seems to offer much more difficulty. On a more less striking scale, the same difficulty is often encountered, namely in plant being very abundant on one spot, with no difference in condition that we can perceive, & not found within many miles of it, but not found anywhere

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197 78 / 172 64

else in the district or even Kingdom, & yet without any perceptible difference in the conditions: These, however, are exceptional though not very rare cases, the common rule bei apparently being that very local plants or animals (*Al. De Candolle. Geograph. Bot. p. 470) are few not numerous in individuals.

But the most case fact which has struck me the most, is that given by Alph. De Candolle, that certain some few "social plants" are social* (a) to the extreme limits of their range, or are not thinly scattered as might be expected, & when consequently we must suppose that the conditions have begun to be unfavourable. If social plants could help each other like some social plants animals, whence from which the term social has been borrowed, there would be no difficulty, for then as far as they could range, they would range in company. But there seems to be no essential difference, only one in degree, between a social plant, & one totally numerous on any one site. Al. De Candolle has shown in his admirable discussion on this subject, (Geograph. Bot. p. 470) that most social plants are thus inhabiting very peculiar or unfavourable sites as salt-marshes, heaths, arctic regions, beneath water &c, & where the natu consequently as only few plants can grow there peculiarly adapted plants grow together in great numbers. Hence, also, in islands, inhabited

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* Geograph. Bot. p. 462. M. De Candolle instances the Cistus & Lavenders &c on the plains in the south of France: some alpine plants: & forests of trees in the Arctic regions.

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suppose a great loss by slugs or other animals. We must bear in mind that in all probability that this will not be the sole check; a certain percentage of seed, for instance, with perishing by not getting buried &c. Now from a thousand

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by only few species, they are very apt to be social; as they are wherever the conditions are very uniform. But the fact which has seemed to me to show that there is no essential difference between very common plants & social plants, is that some naturalised plants are imminently social in their adopted country, —as is eminently the case with the cardoons & thistles on the plains of La Plata, & not, as far as I can make out, in their native home. Nevertheless it seems to me that many plants, both those commonly called social, & those abounding in numbers in some one spot & not elsewhere found in the neighbourhood or even in the whole world, may be said, in a somewhat strained sense, to help each other, so that if they did not live in numbers, they could not live all.—

It follows from the doctrine of the struggle of nature for existence that every plant destroyed is checked in its increase in the seed, seedling, or mature state. For simplicity let us suppose in any plant that the main check falls on the seed, owing to its being devoured by some bird or insect: the argument will be just the same if applied to the seedling & we suppose a great less by slugs, or larvæ of insects &c or other to any animal. Now if from a thousand on ten thousand

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Individual plants of the same plant kind  plants of the same kind growing together, there will be a far better chance of many seeds being preserved, if the birds or animals which feed in it, than from singular a few dozen plants,—that is as long as the increase of the bird or insect which preys on the seed in question have not their minimum numbers is checked by some other agency & is not determined by the seed of the plant in question: if with the increase in seed the numbers of its devourers increased in the same ratio, then it would make no difference in the proportion saved whether there were a thousand or a dozen of the plants; but if the devouring th birds or insects could not thus increase, owing to the want of food in winter, or fr owing to being preyed on by other animals &c, then & this would very often be the case, then there would obviously be more seed saved from the thousand plants than from the dozen.—We see this often most clearly practically illustrated; a farmer notices a peculiar ear of wheat, & plants the seed in his garden, but it is notorious that without he carefully protect his dozen wheat plants, he will hardly save a seed owing to sparrows: I have seen this occur & in the same year: I raised some hybrid Radishes & with all sorts of protection had the greatest difficulty

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in saving a few seed out of thousands of pods from the attacks of another bird, the green-finch.—Yet in a field large plot of seed Radishes or in a field of wheat, there is of course no difficulty in getting plenty of seed can be secured. Beyond a doubt if radishes & wheat could sow themselves, there would be great difficulty in a small colony of radishes or wheat establishing itself in my garden, supposing that they could sow themselves.

In animals we have seen the same thing occur in small colonies naturally of foxes & antelopes naturally as both being establishing themselves as described by Sir John Richardson, in N. America, though these instances occurred near the limits of their range.)

(Another & quite distinct cause may come into play in determining that without a social plant could not exist beyond the limit in which the conditions were so highly favourable, that large numbers could grow together: that is in dioicous plants there must be at least two individuals near each other, & if the fertilisation of the plant be due to the wind, & not to insects, bearing in mind that they will be planted by chance, it seems almost necessary that there should be a good many together in order to be thoroughly fertilised & produce their full complement of seed. (a) Now we have seen in the third chapter that there is good reason to believe that many

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(a) I have previously shown in our third chapter that many trees are dioicous & monoicous, & they are apt to be social.

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plants are what Sprengel called dichogamous; & when the fertilisation is not aided by the voluntary flight of insects, these could succeed seed well only when growing in masses: I believe many Grasses are in this predicament, namely depending to a great extent on other individuals for their fertilisation; & are not visited by insects; & grasses are apt to be commonly social.

 

From these two considerations, more especially the first one, (& it is likely there are other considerations overlooked by me) I think we can to a certain extent see why a plant (a) or animal may exist in num large numbers in one spot & not spread; for when once established in numbers it might escape destruction by its enemies, but when thinly scattered in colonies, owing to the severe struggle going on all might well be easily perish. Hence this fact which seems at first paradoxical, & is so if we look chiefly to climatal or soil conditions of climate & soil as of predominating influence, ceases to be a paradoxical when we look at all organic beings as periodically incess incessantly struggling together for existence with their utmost energy against their enemies. Authors have often spoken of the occupation of the soil, as a powerful

[62v]

(a) May, or rather must, exist socially in numbers together, or be social, even near the confines of its range, if it can exist at all: we can, also, see why a plant or animal may exist in

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element in distribution: in the strict sense of the word, I think it can be have very little influence; word, if we remember that plants undergo a natural rotation & that seeds are disseminated in a multitude of ways, I think it can have very little influence: in the sense above given, namely that plants or animals when once established in numbers, by their very numbers escape destruction, I have no doubt this occupation is potent.

Another class of facts seemed at one time to me opposed to there being a severe struggle in nature; namely animals having recovered in a state of nature from severe injuries, as evidenced by the fossil Hyaena* (Phil. Transact. 1828. p. 85) which had part of its upper jaw entirely worn away; or by the famous Mylodon described by Owen with a fractured skull. Mr. Couch caught a cod-fish with no eyes, yet in good condition (Transact. Linn. Soc. Vol. XIV p. 72). (a) Lame birds have been noticed for several years building in the same nest. Birds, more especially rooks, have not very rarely been observed with their beak upper & lower mandibles crossing & distorted; & this has been observed even in the case of a

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(a) Mr. Blyth mentions som two nearly blind Indian crows; but these very singularly were fed by other members of the flock.— Rengger describes rickety Jaguars with short legs as not very uncommon in Paraguay.

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Woodpecker (Picus erythrocephalus) which one would have thought would have most severely suffered from such a malconformation.* (Mr. Blackwall Researches in Zoology has collected many several cases, p. 173-6: see also Transact. Linn. Soc. Vol. 15, Part I, p. 9).

But All these cases show only that the struggle for existence is periodical & not incessant, but periodical of which fact we have plenty of other evidence: in the first very severe winter the rooks with the crossed bills would no doubt be cleared off.—

In some cases the term struggle is not very appropriate; for instance in the Misseltoe (Viscum     ); as it can hardly be said to be struggle with any other beings, though evidently dependent on them: if it increased in an inordinate degree it would greatly injure the few trees on which it can grow: it would probably be actually exterminated if the Thrush genus which it helps to feed became extinct; & Kölreuter has shown that its. fertilisation is dependent on certain insects: probably deficient means of dispersal is a principal check in this case.

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Fish of the Shark family (Squalidæ) The Picked Dog-fish (Squalus acanthias) actually swarms on many coasts & yet produce but few young; thus the Picked dog-fish (Squalus acanthias) is said to lay only six young eggs; whereas the Cod-fish sometimes lays above three million & a half. of eggs (*Yarrell British Fishes vol. 2. p. 401; Fleming's Philosophy of Zoology vol. 2 p. 356.) Again many Diptera increase at such a rate, that Linnæus has stated that three flies of Musca vomitoria would devour a horse as quickly as a Lion:2 yet there are other flies, which produce only a single egg, or rather pupa, at a birth & probably in their whole life, and yet such flies

(F. Walker thought so)

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Finally I must allude to an opinion, which I have repeatedly seen advanced, but probably often without deliberation;—namely that the numbers of any species is depend on the number of its eggs or seed, & consequently not on th a struggle for existence at some period of its life (a) In The number of the eggs is no doubt one element in the result but by no means one of the most important. How many rare fish there are existing in very scanty numbers, yet annually producing thousands of ova! years ago I was struck with this in finding a very rare large sea-slug at (Doris) at the Falkland Isld , very rare & yet on calculating the number of the eggs of one individual, I found six hundred thousand. The Condor lays only two eggs & yet in parts it is quite as common, (for I have seen between twenty & thirty take flight from one cliff) as the british American Rhea, which lays between twenty & forty eggs & even more & yet is not so very numerous: but we need not go so far, the Sylv Kitty-wren, (Sylvia troglodytes) lays on an average just twice as many eggs as the other British wrens or Sylviadæ, yet we see no corresponding relation in numbers. But the most striking cases is in certain Diptera flies; of which it has been remarked that they can increase so

[65v]

(or its parents' lif lives

[65v1]

Put a remark that fertility is most important in rapidly increasing but not in final results. This is crucial difference. In the ultimate number no doubt other elements are far from unimportant.

[65v2]

(a) This belief has probably arisen from the larger animals, which cannot can seldom be supported in very great numbers in any country, producing few young; but most of them can protect their young; nor is this relation invariable, as we see in the Crocodile, & amongst Birds in the ostrich.

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rapidly, that the progeny of a single fly would soon devour more than a Lion; yet there are other viviparous flies, which produce only two young in their whole life, & yet are by no means rare, as all who have had their horses tormented by the horse-fly, (Hippobosca) must well known. Amongst plants, I have looked through lists, in which a few of the most abundant plants of a country are marked, & have often noticed amongst them some portion, which produce a the bearers of the fewest number of seeds. But the most conclusive evidence of all — [illeg] seen in may be derived from fossil tertiary shells; we have many numerous cases of a shell formerly rare & now common in the same region, or the reverse case; & I presume no one will suppose imagine that these shells laid a different number of ova varied differed at the two periods. There is an old Eastern fable that the locust lays 99 ninety-nine eggs, but that if it laid the hundredth it would overrun the world; this fable in its philosophy is probably as false as it is old.—

Upon the whole none of the facts, which seem at first to deny that all organic beings have at some period or during some generation to struggle for

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life are of much weight; on the other hand the several remarks & illustrations given in the foregoing pages, imperfect as they are, appear to me conclusively to show that such struggle, often a very complex nature, does truly exist. I have found myself that much reflexion is necessary fully to realise this struggle & dependence of one being on another: our great ignorance of the complete biography of any one single plant or animal makes us slow to believe in the multiform & often extremely obscure checks to their increase. Look at any piece of wild ground, & notice that hundreds, often thousands of seeds annually produced by each plant & disseminated by a hundred ingenious contrivances; —think of the number of eggs produced by each insect, worm & snail,—each animal strives to live, each plant will live if it can,— & yet the average number cannot possibly long increase: go from spot to spot, till you reach the confines of life, & the same story is predetermined. Everywhere, the rate of increase,

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if unchecked, will be geometrical; whilst the means of subsistence on the long average will be constant; & we know in our slow-breeding larger domestic animals, under a favourable union economy how high large & rapid the result of this ratio has been in an unstocked country. We must regret that sentient beings should be exposed to so severe a struggle, but we should bear in mind that the survivors are the most vigorous & healthy, & can most enjoy life: the struggle seldom recurs with full severity during each generation: in many cases it is the eggs, or very young which perish: with the old there is no fear of the coming famine & no anticipation of death. Philosophical writers, such as Lyell, Hooker* Herbert &c have shown how fully they most ably endeavoured to make others appreciate the struggle & equilibrium of life, as clearly as they do themselves; & I should not have discussed this subject at length in at length, had it not been in many ways of great importance for us; & had I not occasionally met with-good observers of nature, who by such remarks,-as that the number of the individuals of a species was dependant determined by the number of its eggs it laid:—or that when an island partly subsides into the

[68v]

* Hooker & Thomson Flora Indica: see the remarks in Introduction p. 41.

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ocean, it will become (as if not already) (as if not already) crowded in an extraordinary degree with living beings,—show as it seems to me, an entire ignorance of the real state of nature. Nature may be compared to a surface covered with ten-thousand sharp wedges, many of the same shape & many of different shapes representing different species, all packed closely together & all driven in by incessant blows: the blows being here & there far severer on some at one time than at another; sometimes a wedge of one form & sometimes another being struck; the one driven deeply in forcing out others; with the jar & shock often transmitted very far to other wedges in many lines of direction: beneath the surface we may suppose that there lies a hard layer, fluctuating in its level, & which may represent the minimum amount of food required by each def living being, & which layer will be impenetrable by the sharpest wedge.

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(Ch. 5 Corollary on Structure in relation to other organism)

Corollary on the relation in Structure of organic beings. It follows almost necessarily from what we have seen of the struggle for existence, dependent on the habits of animals & plants, that the structure of each organic being stands in most intimate relation to that of other organisms. For habit structure habit generally goes with structure, notwithstanding that in most great families, a few species having the same general structure can be picked out with very aberrant habits in some degree aberrant. It is very important fully to appreciate t in order, as I believe, to understand many facts in geographical distribution, the steps towards extinction, & my the principle of natural selection, fully to appreciate how intimately visible structure, by which we discriminate species from species & genus from genus, is related to the structure of other organic beings. Obviously every living being has s its constitution adapted to the climate of its home; but this seems to produce scarcely any visible difference in structure: (a) Thus species of such tropical genera as the Elephant & Rhinoceros, inhabited during the glacial epoch very cold countries, with no essential difference in organization; for their woolly covering however important for their habits cannot be

[70v]

(a) thus in every kingdom we have a few species keeping identically the same structure under the most opposite climates—look at Poa from Equator to T. del Fuego, up to limit of snow in Cordillera.

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looked at as an important difference in structure.

It has often been noticed that many tropical families of plants send out one or two species, having of course the structures of their family, into the cooler temperate regions; on the other hand, such northern genera as the Rose & willow have each a species inhabiting the hottest plains of India.* (*Hooker, Himalayan Journal vol. 2. p. 255). I presume that many highly succulent & vascular plants are so far related to a hot climate that they could not exist where severe frost would burst their textures; but it would seem that much caution is required in drawing all such conclusions. For instance seeing the vast number of Heaths at the Cape of Good Hope, & hearing. (Drege & Meyer. Zwei Pflanzengeograph. Doc. Flora 1848 B. 2 p. 26) that every family of plants of modest size, even leguminous & compositous plants, there have there some & often many species with heath-like foliage, it would appear a safe induction that heath-like leaves were related to a dry & moderately hot climate; yet our heaths inhabit damp & cold mountains. We find animals & plants

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inhabiting the most abnormal stations, as hot retains & sulphureous springs & deep caverns into which a ray of light never enters penetrates, & yet not displaying any great difference in structure from species of the same genera inhabiting ordinary stations.

Whether an animal or plant shall lives, breathes or moves on land, air or water certainly influences the structure in a visible & most important manner; but even in these cases there is a secondary & perhaps equally important relation to the coinhabitants of the same element. whether the one case obtain food & escape its enemies. Whether an animal feeds on vegetable or animal food, obviously plainly influences structure, though here the relation is between organic beings, either dead alive or dead, & often of a special nature. Moreover if we run over in our mind the various structures of the commoner animals, we shall see that the manner of obtaining their prey or food & of escaping danger from other living beings is almost equally influential on their visible  structure.)

But (As the relation of plants in their visible structure to other organic beings is not so obvious as in animals, I will briefly run through the life of a plant in

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the abstract, & which will serve as a summary for parts of this chapter. Beginning with the flower, which has its dangers from flower-feeding beetles &c, I cannot doubt from the facts given in our third chapter, that the beauty of the colo corolla, the scent in night-bloomers, the positions of the nectary & of the stamens & pistils to each other stand in many cases in direct relation to insects of special genera & classes.

When the seed is matured, what a animals in multitudes of animals prey on it; & it will escape destruction by its size, hardness, defences, chemical nature or mere number. Its dispersal in some cases depends partly on hooks or on agreeable pulp: even the down of a thistle is perhaps important to it, in as much as the ground is thickly covered by other plants & thickly sown every year: under this same relation the period to other plants, the period & rapidity of germination will be all important. So again the amount of nourishment surrounding the embryo within the seed, we may believe is given to certain plants that in their earliest days they may succeed in struggling with other plants. The seedling has its special enemies as has the mature plant, which

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sometimes defends itself from-animals by prickles, more often by its chemical natur composition, & which often gains the day over other plants by rapid growth or mere height, at the same time protecting & shadowing other plants, & feeding them with its decayed leaves.

One set of plants will allow another set to live only on some bare chalk banks though, though not well perfectly suited to them; but the relation of different plants to each other growing on the same plot of ground must be equally important. Cut a piece of turf & look at the inextricable mass of roots, each growing rapidly in the line where it can find food: it is must be like a battle between voracious animals devouring the same prey. The power of a set of each plant in an entangled mass to get its food apparently will depend on their different periods of activity & on the depth & manner of growth of their roots. Each plant requires certain inorganic bases & a certain amount of moisture; but this in many cases will depend as much on other co-existing plants as on the nature of the soil; & for even with regard to moisture one sees in hot summer how the grass though shaded is often dryed up under a tree. To give one example,—

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(Ch. 5 Corollary on Strucutre)

the turnip can beat many weeds from overshadowing them by its rapid growth, & so as farmers say cleans the ground; this rapid growth, I may add, apparently stands in relation to the enormous destruction which this plant suffers during its early state alone from the Haltica & saw-fly. The turnip is said to contain but a small percentage of the salts of phosphorus, yet farmers practically find it adviseable to give it phosphate of lime, owing to its rapid growth, rather than to wheat which has ultimately to assimilate contains a larger percentage of phosphorus, but is a slower grower. So that in amongst plants struggling together in a soil very poor in phosphorus, it is quite possible that one requiring much phosphorus might beat another requiring but little of this substance.)

From these several considerations I think we may safely conclude that a plant or animal if naturalised in a new country, under exactly the same conditions of climate & soil as in its native country; but associated with a different set of organic beings, would in fact be generally placed under quite as new conditions as if the climate had been somewhat different modified. Under an extremely different climate it could would not

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become naturalised. It would probably be quite unimportant to the naturalised organism, whether the greater number of its compatriots were to it new or old forms; but those from above which stood in some relation to it would alone be important, as in the highest degree; & then in the highest degree; & these influential forms might be as different as possible in the scale of nature, but more commonly those not having somewhat similar habits & therefore most commonly only often systematically related forms would be the more important. We may put the case in another point of view; let us in imagination alter the wish to alter the structure or constitution of any being so that its numbers might might increase: without on the confines of its range we should have to change its climatal constitution & in doing this we should not have, judging from analogy now, much to alter its structure; even in the midst of its range, as we see the proportional numbers of the inhabitants of a country are changed according as the season is wet or dry &c, we might in some cases increase its numbers by a similar change: always having to do this without deteriorating in in any respect in the slightest degree its multiform relations to the other in inhabitants of the same place. But these relations are so numerous, so complex & so important that we may imagine believe that it would

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general probably be easier to make some slight change in structure in respect to the other coinhabitants in order to allow its numbers to increase. How totally ignorant we are how this could be effected, we shall immediately perceive, if we ask ourselves what we should alter. In the case of single species of a Family or Order inhabiting a country, or in such cases as the Misseltoe, we can perceive that the altered structure would have to stand in relation to beings systematically far removed: in in the misseltoe we may imagine a greater power of penetrating the bark of the apple, or the see berries being rendered more attractive to birds might aid the misseltoe to increase in numbers but it is all the wildest conjecture. As all countries are inhabited. But

Very commonly the altered structure would have to be in relation to nearly allied forms & here the difficulty of imagining a favourable change of structure is even greater. Would mere increase in size & strength prevent the black rat from yielding in so many quarters of the world to the Norway rat: this is quite doubtful, at least the great size of the occidental Blatta has not saved it from its puny Oriental congeners. What change could we make in the Barn-swallow of the United States to allow it to withstand the inroads of the allied Hirundo fulva? And so we may continue to puzzle ourselves in infinitely numerous cases.)

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(I have discussed this subject at some length, But for it seems to me most important under many points of view, that we should fully realise our ignorance, & never forget, that though the constitution of each being is obviously necessarily related to the climate of its country, yet that not only in animals but in plants, much, probably far the greater part of the structural differences between species & species stands [faint pencil insertion illeg] not only in animals, but in plants, in the most direct yet generally unperceived relation to the other organic coinhabitants beings of the same country.