Origin of Species Variorum

Comparison with 1869

answer these questions. In the vertebrata, we see a series of internal vertebræ bearing certain processes; in the articulata, the body divided into a series of segments, bearing external appendages; and in flowering plants, spiral whorls of leaves. ↑ An indefinite repetition of the same part or organ is the common characteristic (as Owen has observed) of all low or little-modified forms; therefore ... the unknown progenitor of the vertebrata no doubt possessed many vertebræ; the unknown progenitor of the articulata, many segments; and the unknown progenitor of flowering plants, many leaves arranged in one or more spires. We have formerly seen that parts many times repeated are eminently liable to vary in number and structure. Consequently such parts being already present, and being highly variable, would afford the materials for adaptation to the most different purposes; and they would generally retain through the force of inheritance plain traces of their original or fundamental resemblance. ↑

In the great class of molluscs, though it can easily be shown that the parts in distinct species are homologous, but few serial homologies can be indicated; that is, we are seldom enabled to say that one part .. 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, as we find in the other great classes of the animal and vegetable kingdoms.

answer these questions. In the vertebrata, we see a series of internal vertebræ bearing certain processes and appendages; in the articulata, we see the body divided into a series of segments, bearing external appendages; and in flowering plants, we see a series of successive spiral whorls of leaves. ↑ An indefinite repetition of the same part or organ is the common characteristic, as Owen has observed, of all low or little modified forms; therefore we may readily believe that the unknown progenitor of the vertebrata possessed many vertebræ; the unknown progenitor of the articulata, many segments; and the unknown progenitor of flowering plants, many spiral whorls of leaves. We have formerly seen that parts many times repeated are eminently liable to vary in number and structure; consequently it is quite probable that natural selection, during a long-continued course of modification, should have seized on a certain number of the primordially similar elements, many times repeated, and have adapted them to the most diverse purposes. And as the whole amount of modification will have been effected by successive slight steps, we need not wonder at discovering in such parts or organs a certain degree of fundamental resemblance, retained by the strong principle of inheritance. ↑

In the great class of molluscs, though we can homologise the parts of one species with those of other and distinct species, we can indicate but few serial homologies; that is, we are seldom enabled to say that one part or organ is homologous with another 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, as we find in the other great classes of the animal and vegetable kingdoms.