4IO A HISTORY OF BIRDS 



to this puzzling subject, and some of these have brought to 

 light stages which show that where eutaxic wings are met with 

 in diastataxic groups — Pigeons, Kingfishers, Swifts — this eutaxy 

 has been secondarily acquired. The primitive was undoubtedly 

 eutaxic. This view is not, however, held by the author just 

 quoted. 



The subject presents many difficulties in the way of investi- 

 gation, and so far seems to defy solution. Hence it is but 

 briefly referred • to here, by way of adding to the number of 

 structural characters which seem outside the pale of the action 

 of selection, which seem in short to have no relation to the 

 problem of the struggle for existence, for it is commonly as- 

 sumed that all tangible characters owe their existence to this 

 factor. Those who desire to inquire further into this mystery 

 will find all the information so far gathered together in two 

 papers published in vol. xxvii. of the Journal of the Linnean 

 Society by Mitchell and Pycraft. 



