" AQUINTOCUBIIALTSM " IN THE BIRD's WING, 253- 



series, and is always much shorter than these. The Megapodes 

 as we have just remarked, are diasta-, and the Grame-birds 

 eu-taxic. If the two are closely related, we might claim justifica- 

 tion in holding that the arrested development of the 1st cubital 

 remex was derived from a common source, and that diastataxy 

 has been acquired by the Megapodes since then. If this inter- 

 pretation be correct, it follows that we may hold it to be 

 admitted that diastataxy may have arisen independently in 

 different groups of birds, — a somewhat unlikely conclasion. The 

 position into which we have drifted, then, may be stated as 

 follows : — 



The Class Aves, very early iu the process of its differentiation, 

 developed the phenomena of diastataxy, which has been retained 

 by very different groups now regarded as only remotely allied. 

 The presence of eutaxic forms in an undoubtedly diastataxic 

 group, as in the case of Golumhida, must be regarded as the 

 result of a secondary re-arrangemeni; of the wing-feathers, or as 

 a reversion to the more primitive type of wing from which it was 

 derived. Such admittedly aberrant eutaxic forms as Psophia, 

 Cariama, Heliornis, must be regarded as more remotely allied 

 to the diastataxic forms with which they are now associated 

 than is generally believed. Diastataxy is probably an indication 

 of consanguinity. 



There are certainly difficulties in the way of acceptance of this 

 view, perhaps the most formidable being the case of the Swifts 

 and Kingfishers, the majority of which are eutaxic ; some 

 genera, moreover, containing both eu- and diasta-taxic forms. 

 We have to face two alternatives : — 



(1) That the group, whichever it may be, really belongs to 



the diastataxic stock, but that the majority of the species, 

 like Columhula, have reverted to eutaxy ; or, 



(2) That diastataxy must be explained, in that and all other 



groups, as the result of the action of similar mechanical 

 forces, upon a common type, and which may occur inde- 

 pendently in different groups, and even different species 

 of the same genus. 



In spite of the objections which we may feel towards the first 

 proposition, it seems more probable than the second, and more 

 in harmony with the facts as a whole. 



