On so-called “Quintocubitalism” in the Wing of Birds; with special reference to the Columbae, and Notes on Anatomy.

Abstract

Summary The Columbae, which have been regarded hitherto as a diastataxic group, have several members with the eutaxic condition. Comparison of the featheriog in these form makes it probable, or at least plausible, that the eutaxic condition has been attained by cloaing up of the gap, with first crowding, and then disappearauce, of two of the three feather8 occupying the primitive gap. Intermediate stages between true wide-gapped diastataxic forms and true eutaxic forms occur. Comparison of the anatomy of the eutaxic forms with that of the diastataxic forms shom that the former are on the whole more advanced in the general progressive modification of the whole group. It is easy to show that in a hypothetical pentadactyle wing a gap in specialized rows of incipient quills might arise in the position required for the diastataxic gap. Among Aves there is a gerierltl correspondence with the conditions aniong Columbae. The diaatataxic condition of the wing is primitive aniong birds; it is the architaxic condition. By c!osing up of the ranks any architaxic wing may become eutaxic, and this change has beell mRde by some whole groups and by individuals of other groups.