only in a slight degree, it is not probable that they should vary at the present day.

On the other hand, the points in which species differ from other species of the same genus are called specific characters; and as these specific characters have varied and come to differ since the period when the species branched off from a common progenitor, it is probable that they should still often be in some degree variable — at least more variable than those parts of the organisation which have for a very long period remained constant.

9. Secondary Sexual Characters Variable

I think it will be admitted by naturalists, without my entering on details, that secondary sexual characters are highly variable. It will also be admitted that species of the same group