Origin of Species Variorum

are reversions to a formerly existing character, and what are new but analogous variations, yet we ought, on our theory, sometimes to find the varying offspring of a species assuming characters (either from reversion or from analogous variation) which already are present in other members of the same group. And this undoubtedly is the case. .. ..

A considerable part of the difficulty in recognising in our systematic works a variable species, is due to its varieties mocking, as it were, ... other species of the same genus. A considerable catalogue, also, could be given of forms intermediate between two other forms, which themselves can only doubtfully be ranked as ... species; and this shows, unless all these forms be considered as independently created species, that the one in varying has assumed some of the characters of the other, so as to produce the intermediate forms. But the best evidence is afforded by parts or organs of an important and generally uniform nature occasionally varying so as to acquire, in some degree, the character of the same part or organ in an allied species. I have collected a long list of such cases; but here, as before, I lie under the great disadvantage of not being able to give them. I can only repeat that such cases certainly do occur, and seem to me very remarkable.

I will, however, give one curious and complex case, not indeed as affecting any important character, but from occurring in several species of the same genus, partly under domestication and partly under nature. It is a case almost certainly of reversion. The ass sometimes has very distinct transverse bars on its legs, like those on the legs of the zebra: it has been asserted that these are plainest in the foal, and, from inquiries which I have made, I believe this to be true. ↑ The stripe on the shoulder is sometimes double and is very variable in length and outline.