Origin of Species Variorum

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

The embryos, also, of distinct animals within the same class are often strikingly similar: a better proof of this cannot be given, than a circumstance mentioned by Agassiz, namely, that having forgotten to ticket the embryo of some vertebrate animal, he cannot now tell whether it be that of a mammal, bird, or reptile.

→ immature 1869 1872

first and second 1859 1860 1861 1866

→ young of the thrush 1869 1872

thrush 1859 1860 1861 1866

→ when adult are 1872

are 1859 1860 1861 1866 1869

→ or spots can 1861 1866 1869 1872

can 1859 1860

→ lion and the puma. 1861 1866 1869 1872

lion. 1859 1860

birds, lizards, and snakes, probably also of chelonia, are in their earliest states exceedingly like one another, both as a whole and in the mode of development of their parts; so much so, in fact, that we can often distinguish the embryos only by their size. ↑ In my possession are two little embryos in spirit, whose names I have omitted to attach, and at present I am quite unable to say to what class they belong. They may be lizards or small birds, or very young mammalia, so complete is the similarity in the mode of formation of the head and trunk in these animals. The extremities, however, are still absent in these embryos. But even if they had existed in the earliest stage of their development we should learn nothing, for the feet of lizards and mammals, the wings and feet of birds, no less than the hands and feet of man, all arise from the same fundamental form." The larvæ of most crustaceans, at corresponding stages of development, closely resemble each other, however different the adults may become; and so it is with very many other animals. A trace of the

jaw

law

of embryonic

resemblance,

resemblance

sometimes

occasionally

lasts till a rather late age: thus birds of the same genus, and of

closely

....

allied genera, often resemble each other in their →immature plumage; as we see in the spotted feathers in the →young of the thrush group. In the cat tribe, most of the species →when adult are striped or spotted in lines; and stripes →or spots can be plainly distinguished in the whelp of the →lion and the puma. We occasionally though rarely see something of

this

the same

kind in

plants:

plants;

thus the

embryonic

first

leaves of the ulex or furze, and the first leaves of the

phyllo- dineous

phyllodineous

acaceas,

acacias,

are pinnate or divided like the ordinary leaves of the

leguminousæ.

leguminosæ.

The points of structure, in which the embryos of widely different animals

within

the same class resemble each other, often have no direct relation to their

condi- tions

conditions

of existence. We cannot, for instance, suppose that in the embryos of the vertebrata the peculiar loop-like

course

courses

of the arteries near the branchial slits are related to similar conditions,— in the young mammal which is nourished in the womb of its mother, in the egg of the bird which is hatched in a nest, and in the spawn of a frog under water. We have no more reason to believe in such a relation, than we have to believe that the

same

similar

bones in the hand of a man, wing of a bat, and fin of a porpoise, are related to similar conditions of life. No

good observer

one

will

....

suppose

supposes

that the stripes on the whelp of a lion, or the spots on the young blackbird, are of

~~any~~

any

use to these

animals,

are

the

conditions

which

they

are

exposed.

The case, however, is different when an animal during any part of its embryonic career is active, and has to provide for itself. The period of activity may come on earlier or later in life; but whenever