Origin of Species Variorum

→ circumstance mentioned by Agassiz, 1859 1860

statement made by Von Baer, 1861

→ having forgotten to ticket the 1859 1860

"the 1861

→ some vertebrate animal, he cannot now tell whether it be that of a mammal, bird, or reptile. 1859 1860

mammalia, of 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. 1861

↑ 4 blocks not present in 1859 1860; present in 1861 1866 1869 1872

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."

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

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.

→ life. 1859 1860 1861

life sometimes differ much from each other. 1866 1869

→ first and second 1859 1860 1861 1866

immature 1869 1872

→ thrush 1859 1860 1861 1866

young of the thrush 1869 1872

→ are 1859 1860 1861 1866 1869

when adult are 1872

→ can 1859 1860

or spots can 1861 1866 1869 1872

→ lion. 1859 1860

lion and the puma. 1861 1866 1869 1872

→circumstance mentioned by Agassiz, namely, that →having forgotten to ticket the

embryos

embryo

of →some vertebrate animal, he cannot now tell whether it be that of a mammal, bird, or reptile. ↑ ↑ The vermiform larvæ of moths, flies, beetles,

&c.,

generally resemble

resemble

each other much more closely than do the mature insects; but in

these

the

cases

case

~~of larvæ,~~

of larvæ,

the embryos are active, and

from having

have

been adapted for special lines of →life. A trace of the

jaw

law

of embryonic

resemblance

resemblance,

occasionally

sometimes

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

~~closely~~

closely

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

the same

this

kind in

plants;

plants:

thus the

first

embryonic

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

phyllo- dineous

phyllodineous

acacias,

acaceas,

are pinnate or divided like the ordinary leaves of the

leguminosæ.

leguminousæ.

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

courses

course

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

similar

same

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~~

will

supposes

suppose

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