2M ME. W. p. PYCEAFX ON SO-CALLED 



Explanations of Diast ataxy . 



The first recorded reference to diastatasy is that of Gerbe (3),^ 

 who describes it in the following words : — " Chez les Eapaces, les 

 Pigeons, les Echassiers, les Palmipedes, il y a atropbie complete 

 de I'une des remiges secondaires, et cette atrophic, qui parait 

 etre originelle, porte invariablement sur la cinquieme. Ses 

 satellites, c'est-a-dire, sa couverture superieure et sa couverture 

 inferieure, prennent un developpement normal et occupent leur 

 place respective, comme si elles accompagnaient la penne qui fait 

 defaut. 



" Ni les vrais Passereux, ni les Zygodactyles (les Perroquets 

 exceptes) ne pr^sentent cette singuliere anomalie." 



My friend and late colleague, Mr. E. S. Groodrich, the 

 Aldrichian Demonstrator of Comparative Anatomy at Oxford, 

 took part with me for some time, in this investigation, and 

 also formulated a theory of his own to account for the con- 

 ditions which have been described and figured in this paper, 

 and in justice to him, as well as because of its intrinsic value, I 

 propose to endeavour to describe his theory here. 



Briefly, he holds that the phenomena of diastataxy are due to a 

 bifurcation of a row of feather-papillae, probably the second 

 — major coverts — starting at what is now the 5th major 

 covert. Thus a double row was formed representing the present 

 major and median coverts 1-5. This theory does not demand 

 either shifting of remiges or coverts. Supposing the shifting of 

 the former be proved, the presence of this " intercalary row," as 

 he termed what are now major coverts 1-5, is still more easily 

 understood. They have appeared to fill u]3 the space between the 

 row immediately in front and the remiges behind. Bifurcation 

 of this kind occurs in the scale-covered forearm of Eeptiles for 

 instance : or, again, in the form of additional rows of ossicles in, 

 the manus of Ichthyosaurs. 



Yet another attempt to solve this mystery is that of Degen 

 (1). Though none will grudge this writer the credit of having 

 evolved a very ingenious hypothesis, few probably will be found 

 willing to adopt it. Degen carries us back to an imaginary 

 quadri-dactyle manus in which each digit supported a set of 

 remiges and major coverts. In course of time the 4th digit 

 became suppressed and its remiges, 3 in number, migrated 



