Origin of Species Variorum

→ by beasts of prey to 1869

to 1859 1860 1861 1866

↑ 3 blocks not present in 1859 1860 1861 1866 1869; present in 1872

It appears probable that disuse has been the main agent in rendering organs rudimentary. It would at first lead by slow steps to the more and more complete reduction of a part, until at last it became rudimentary,— as in the case of the eyes of animals inhabiting dark caverns, and of the wings of birds inhabiting oceanic islands, which have seldom been forced by beasts of prey to take flight, and have ultimately lost the power of flying. Again, an organ, useful under certain conditions, might become injurious under others, as with the wings of beetles living on small and exposed islands; and in this case natural selection will have aided in reducing the organ, until it was rendered harmless and rudimentary.

→ structure and function, 1869 1872

function, 1859 1860 1861 1866

→ An organ, 1859 1860 1861 1866 1869

Organs, originally formed by the aid of natural selection, 1872

→ originally formed by the aid of natural selection, when 1869

when 1859 1860 1861 1866 1872

↑ 1 blocks not present in 1859 1860 1861 1866 1869; present in 1872

All this agrees well with what we see under nature.

→ has to exert 1869 1872

to 1859 1860 1861 1866

→ reproduce 1859 1860 1861 1866 1869

tend to reproduce 1872

→ mature age, but 1869 1872

age, and consequently 1859 1860 1861

age, but 1866

→ size of rudimentary organs in the embryo relatively to its other parts, 1869

relative size of rudimentary organs in the embryo, 1859 1860 1861 1866

size of rudimentary organs in the embryo relatively to the adjoining parts, 1872

→ the rudimentary part would tend 1869

(as we have good reason to believe 1859 1860 1861 1866

→ OMIT 1869

possible) the rudimentary part would tend to be 1859

possible), the rudimentary part would tend to be 1860 1861 1866

→ the economy of organisation, 1869

economy, 1859 1860 1861

economy 1866

→ explained in 1859 1860 1861 1869

in organisation, explained in 1866

organs, until they have become rudimentary,— as in the case of the eyes of animals inhabiting dark caverns, and of the wings of birds inhabiting oceanic islands, which have seldom been forced →by beasts of prey to take flight, and have ultimately lost the power of flying. Again, an organ useful under certain conditions, might become injurious under others, as with the wings of beetles living on small and exposed islands; and in this case natural selection would continue slowly to reduce the organ, until it was rendered harmless and rudimentary. ↑

Any change in →structure and function, which can be effected by

~~insensibly~~

insensibly

small

stages,

steps,

is within the power of natural selection; so that an organ rendered,

during

through

changed habits of life, useless or injurious for one purpose, might

easily

....

be modified and used for another purpose.

Or an

organ

might

might,

also, be

retained for one alone of its former functions. →An organ, →originally formed by the aid of natural selection, when rendered

useless

useless,

may well be variable, for

their

its

variations

cannot

can no

longer be

checked by natural selection. ↑

Moreover, at

whatever period of life

disuse

either disuse

or selection reduces an organ, and this will generally be when the being has come to maturity and →has to exert its full powers of action, the principle of inheritance at corresponding ages will →reproduce the organ in its reduced state at the same →mature age, but will seldom affect

or reduce

....

it in the embryo. Thus we can understand the greater →size of rudimentary organs in the embryo relatively to its other parts, and their lesser relative size in the adult. But if each step of the process of reduction were to be inherited, not at

the

corresponding age, but at

an extremely

a very

early period of

life

life,

→the rudimentary part would tend to be →OMIT wholly lost, and we should have a case of complete abortion. The principle, also, of →the economy of organisation, →explained in a former chapter, by which the materials forming any

part

part,

or structure,

....