244 ME. W. P, PTCEAPT ON SO-CALLED 



these we must seek for confirmation o£ the course of development 

 outlined in the case of the Plover and Guillemot. 



In the Pigeon's wins^ (PI. 15. fig. 1) the feather rudiments 

 have arranged themselves in strongly marked, transversely-oblique 

 rows sloping inwards and presenting a strongly curved front 

 towards the distal end of the wiag. As yet, there are but faint 

 traces of the marginal coverts. It is noteworthy that the trans- 

 verse rows of coverts from 1-5 are more widely separated one 

 from the other than is the case with the more proximal rows. 

 The downward shifting of the anterior remiges and their coverts 

 (1-5) is very marked. The intercalary row is the 3rd. This last 

 is well seen in the wing of the nestling (PI. 16. fig. 1). 



In the wing of the Duck (Anas hoscas var. domestica), PL 15. 

 fig. 3, the intercalary is formed by the 3rd row of coverts, 

 i. e. 1-5 of the minor coverts. There are faint traces of several 

 more rows in addition to those in the figure. Compared with the 

 adult wiug, one very striking fact becomes apparent. It will' 

 be noticed that in the embryo wing (PI. 15. fig. 3) the 1st 

 inedian covert — that lying immediately above the first cubital 

 remex and its major covert- — ^lies over the base of metacarpal 

 II., whilst the 2nd median covert lies just below the angle 

 between the carpus and the distal end of the ulna. In the 

 adult this spot comes to be occupied by the 1st median covert, 

 that is to say, it apparently supplants the 2nd and takes 

 its place. From this it would seem that we have indeed 

 evidence of an increased lengthening of the forearm which can 

 be measured by the distance from the 2nd to the 1st median 

 covert. 



A possible Objection. 



Diastatasy, as we have endeavoured to show, is due, not as 

 was supposed, to the loss of the 5th cubital remex, but to the 

 shifting of the reunites and coverts lying to the outer side of this. 

 The ultimate fate, however, of the remex in question has so far 

 only been hinted at. Exactly what takes place during this 

 shifting is difileult to make out, and will only be possible after a 

 larger series of embryos have been examined. This much, how- 

 ever, seems certain, — that all the covert-feathers of the wing 

 from the 6th inwards have moved outwards, one place, in the 

 form of a series of obliquely transverse rows. Thus the trans- 

 verse row which origiuall}'' belonged to the 6th remex now 



