Origin of Species Variorum

can be given. But on the view that species are only strongly marked and fixed varieties, we might .. expect to find them still often continuing to vary in those parts of their structure which had varied within a moderately recent period, and which had thus come to differ. Or to state the case in another manner: — the points in which all the species of a genus resemble each other, and in which they differ from ... allied genera, are called generic characters; and these characters in common I attribute to inheritance from a common progenitor, for it can rarely have happened that natural selection will have modified several species, fitted to more or less widely-different habits, in exactly the same manner: and as these so-called generic characters have been inherited from before the period when the different species first branched off from their common progenitor, and subsequently have not varied or come to differ in any degree, or 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.

Secondary Sexual Characters Variable .

In connection with the present subject, I will make only two other remarks. I think it will be admitted, without my entering on details, that secondary sexual characters are very variable; I think it also will be admitted that species of the same group differ from each other more widely in their