Origin of Species Variorum

→ in 1869 1872

of one species with those of another and 1859

of one species with those of other and 1860 1861 1866

→ are homologous, but 1869

we can indicate but 1859 1860 1861 1866

can be shown to be homologous, only a 1872

→ can be indicated; that 1869

that 1859 1860 1861 1866

such as the valves of Chitons, can be indicated; that 1872

↑ 6 blocks not present in 1859 1860 1861 1866 1869; present in 1872

But morphology is a much more complex subject than it at first appears, as has lately been well shown in a remarkable paper by Mr. E. Ray Lankester, who has drawn an important distinction between certain classes of cases which have all been equally ranked by naturalists as homologous. He proposes to call the structures which resemble each other in distinct animals, owing to their descent from a common progenitor with subsequent modification, homogenous; and the resemblances which cannot thus be accounted for, he proposes to call homoplastic . For instance, he believes that the hearts of birds and mammals are as a whole homogenous,— that is, have been derived from a common progenitor; but that the four cavities of the heart in the two classes are homoplastic,— that is, have been independently developed. Mr. Lankester also adduces the close resemblance of the parts on the right and left sides of the body, and in the successive segments of the same individual animal; and here we have parts commonly called homologous, which bear no relation to the descent of distinct species from a common progenitor. Homoplastic structures are the same with those which I have classed, though in a very imperfect manner, as analogous modifications or resemblances. Their formation may be attributed in part to distinct organisms, or to distinct parts of the same organism, having varied in an analogous manner; and in part to similar modifications, having been preserved for the same general purpose or function,— of which many instances have been given.

→ as they now exist, but 1869 1872

but 1859 1860 1861

in their present state, but 1866

→ and simpler element. 1866 1869 1872

element. 1859 1860 1861

→ this having 1869 1872

a modification of this nature having 1859 1860 1861

such modifications having actually 1866

→ According to the views here maintained, such language 1869 1872

On my view these terms 1859 1860 1861 1866

→ OMIT 1869 1872

during a long course of descent 1859 1860 1861 1866

→ though extremely simple legs, is 1869

legs, or from some simple appendage, is 1859 1860 1861

though simple legs, is 1866

though extremely simple legs, is in part 1872

→ subjects in the whole round 1869 1872

departments 1866

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

Herein are included the ordinary metamorphoses of insects, with which every one is familiar.

→ The metamorphoses of insects, with which every one is familiar, 1869

These 1866

parts →in distinct

species,

species

→are homologous, but few serial

homologies;

homologies,

homologies

→can be indicated; that is, we are seldom enabled to say that one part

or organ

....

is homologous with another

part in

the same individual. And we can understand this fact; for in molluscs, even in the lowest members of the class, we do not find nearly so much indefinite repetition of any one

part

part,

as we find in the other great classes of the animal and vegetable kingdoms. ↑

Naturalists frequently speak of the skull as formed of metamorphosed

vertebræ:

vertebræ;

the jaws of crabs as metamorphosed legs; the stamens and pistils

flowers as metamorphosed leaves; but it would in

these

most

cases

~~probably~~

probably

be more correct, as Professor Huxley has remarked, to speak of both skull and vertebræ,

~~both~~

both

jaws and legs,

&c.,—

&c.,

as having been metamorphosed, not one from the

other

other,

→as they now exist, but from some common →and simpler element.

Naturalists,

Most naturalists,

however, use such language only in a metaphorical

sense:

sense;

they are far from meaning that during a long course of descent, primordial organs of any kind— vertebræ in the one case and legs in the other— have actually been

modified

converted

into skulls or jaws. Yet so strong is the appearance of →this having occurred, that naturalists can hardly avoid employing language having this plain signification. →According to the views here maintained, such language may be used literally; and the wonderful fact of the jaws, for instance, of a crab retaining numerous characters, which they

would probably

probably would

have retained through inheritance, if they had really been metamorphosed →OMIT from true →though extremely simple legs, is explained.

Embryology

Development

and

Development .

Embryology.

Embryology .

This is one of the most important →subjects in the whole round of natural history. ↑ →The metamorphoses of insects, with which every one is familiar, are generally