"aquintoctjbitalism: " in the bird's wiifG. 241 



readily constructed by the reader by laying over fig. 1 « a piece 

 of transparent paper and marking over remiges l-4< and coverts 

 from 1-5 in each row. This being done, shift the paper back- 

 wards aud slightly forwards so that the major coverts 1-5 come 

 to lie parallel with the interspace between the remiges and major 

 coverts proximal to 5, as has been done in fig. 1 i. This gives 

 the two broken rows of coverts (major and median) and the 

 intercalary row (3), which exactly agrees with actual wings 

 («. i/., PI. 15. fig. 1). 



Inasmuch as by this artificial mechanical shifting aud re- 

 arrangement of the feathers of the anterior end of the dorsal 

 aspect of the forearm, all the features of the diastataxic wing can 

 be demonstrated, it may be reasonably contended that a strong 

 degree of probability has been brought forward in support 

 of the view that the phenomena of diastataxy are due to a 

 backward and downward shifting of the remiges and their 

 coverts. 



Summary of the foregoing Remarhs. 



To summarize briefly, the contention of the present paper is : — 



(1) That there is no evidence in support of the hypothesis 

 that diastataxy is due to the absence of a remex. 



(2) There is a very considerable amount of evidence to show 

 that a process of shifting has taken place of the coverts and 

 remiges at the distal end of the forearm. This has resulted in 

 carrying remiges ] -4 and the first and each succeeding horizontal 

 row of coverts from 1-5 backwards and slightly downwards and 

 outwards. Thus the original relations between the 5th major 

 covert and its remex have been disturbed, the covert having 

 shifted away from its remex, which has now^ become associated 

 with the 6th covert. Thus the 5th, together with its ventral 

 covert, appears to have lost its remex. 



(3) The cause of this shifting is still a matter for investiga- 

 tion ; it is possibly due to a slight secondary lengthening of the 

 forearm. 



Evidence in support of the above Conclusions. 



We will now proceed to review the evidence in support of the 

 hypothesis just submitted. 



What follows has reference only to the developing remigesr 



LINN. JOUBIf. — ZOOLOaT, TOL. XXTII. 18 



