:252 MB. W. p. PYCKAFT ON SO-CALLED 



The prohahle Origin of the Diastataxic Wing. 



We may now turn our attention to a discussion on the 

 probable origin of diastataxy. 



The primitive wing, I take it, ^as eutaxic, and resembled that 

 of the Common Fowl in that it was clothed by numerous rows 

 •of eovert-featliers ; that of the Picarise and Passeres is a special- 

 ization of a more primitive type, the number of rows of coverts 

 having been reduced. Although, in these, the forearm may have 

 increased in length, the reiniges have decreased in number and 

 become more widely spaced, and have developed broader vaues. 

 Thus an equally efficient wing has been obtained with less 

 -expenditure of material. 



The diastataxic wing is a modification of the eutaxic, and is 

 possibly due to an increase in the length of the wing accom- 

 panied by a corresponding increase in the number of the remiges. 

 It would seem more natural to assume, therefore, that all diasta- 

 taxic wings have been derived from a common source ; and thus 

 this feature may be regarded as a sure sign of affinity, more or 

 less remote, enabling us to classify all birds into groups eu- and 

 diastataxic. 



The existence, however, of what we may term eutaxic genera 

 amongst diastataxic families is certainly a serious difficulty in the 

 way of this hypothesis. Por instance, Columbula is the only 

 known exception amongst the Pigeons, which are diastataxic, 

 though other exceptional genera may turn up, and the numerous 

 instances of diastataxy amongst the Kingfishers and Swifts. It 

 might be pleaded that Columbula has re-acquircd aeutaxialform, 

 by reduction in the length of the wing, and a similar reduction 

 in the number, accompanied by a readjustment of the feathers. 

 Note the position, for instance, of the 5th and 8th remigea in 

 the wings of Columbula and Columba. That this is problematical, 

 howoA^er, is shown by the wing of Ocydromus, which, though very 

 ■greatly reduced in size, still remains diastataxic, like the rest of 

 the Rails. Again, it is probable that the Megapodes, which are 

 diastataxic, are somewhat closely related to the Game-birds, 

 which are eutaxic. Apart from internal anatomy, they present 

 the following points in common : — The remiges, in the nestling, 

 are well developed and functional before the pre-pennse of the 

 trunk are replaced by the definitive contour-feathers. The 1st 

 fiubital remex develops much later in life than the rest of the 



