Origin of Species Variorum

→ OMIT 1872

however slight, in its development, 1859 1860 1861 1866 1869

→ favoured, 1872

seized on by natural selection, 1859 1860 1861 1866 1869

→ would be a decided advantage to each successive individual 1872

by the parasitic habits 1859 1860 1861 1866 1869

→ OMIT 1872

Proteolepas, though effected by slow steps, would be a decided advantage to each successive individual of the 1859 1860 1861 1866 1869

→ to reduce any 1872

in reducing and saving every 1859 1860 1861 1866 1869

→ becomes, through changed habits, 1872

is rendered 1859 1860 1861 1866 1869

→ superfluous, 1859 1860 1861 1872

by changed habits of life superfluous, 1866 1869

→ OMIT 1872

structure of the 1859 1860 1861 1866 1869

→ OMIT 1872

number of the 1859 1860 1861 1866 1869

→ as well as 1872

and 1859 1860 1861 1866 1869

→ As 1872

Inasmuch as this 1859 1860 1861 1866 1869

→ is 1872

seems to be 1859 1860 1861 1866 1869

→ statements accord 1872

remark seems connected 1859 1860 1861 1866 1869

→ which stand low 1872

low 1859 1860 1861 1866 1869

→ here 1872

in this case 1859 1860 1861 1866 1869

less useful,

any

its

diminution,

diminution

→OMIT will be →favoured, for it will profit the individual not to have its nutriment wasted in building up an useless structure. I can thus only understand a fact with which I was much struck when examining cirripedes, and of which many

other

analogous

instances could be given: namely, that when a cirripede is parasitic within another

and

cirripede and

is thus protected, it loses more or less completely

its

own shell or carapace. This is the case with the male Ibla, and in a truly extraordinary manner with the Proteolepas: for the carapace in all other cirripedes consists of the three highly-important anterior segments of the head enormously developed, and furnished with great nerves and muscles; but in the parasitic and protected Proteolepas, the whole anterior part of the head is reduced to the merest rudiment attached to the bases of the prehensile antennæ. Now the saving of a large and complex structure, when rendered

superfluous

superfluous,

→would be a decided advantage to each successive individual of the →OMIT species; for in the struggle for life to which every animal is exposed, each

individual Proteolepas

....

would have a better chance of supporting itself, by less nutriment being

wasted

developing

structure

now

become

useless.

Thus, as I believe, natural selection will

always succeed

tend

in the long run →to reduce any part of the organisation, as soon as it →becomes, through changed habits, →superfluous, without by any means causing some other part to be largely developed in a corresponding degree. And, conversely, that natural selection may perfectly well succeed in largely developing

any

organ,

organ

without requiring as a necessary compensation the reduction of some adjoining part.

Multiple, Rudimentary, and Lowly-organised Structures are

Variable .

....

It seems to be a rule, as remarked by Is. Geoffroy St. Hilaire, both

with

varieties and

....

species, that when any part or organ is repeated many times in the →OMIT same individual (as the vertebræ in snakes, and the stamens in polyandrous flowers) the number is variable; whereas the →OMIT same part or organ, when it occurs in lesser numbers, is constant. The same author →as well as some botanists have further remarked that multiple parts are

also very

extremely

liable to

variation

vary

in structure. →As "vegetative repetition," to use Prof.

Owens

Owen's

expression, →is a sign of low

organisation;

organisation,

the foregoing →statements accord with the

very general

common

opinion of naturalists, that beings →which stand low in the scale of nature are more variable than those which are higher. I presume that lowness →here means that the several parts of the organisation have been but little specialised for particular functions; and as long as the same part has to perform diversified work, we can perhaps see why it should remain variable,