142 



Degeneration in the Ostrich 



is situated in the marginal row. It is evident therefore that the de- 

 generative influence has not yet reached the first row of coverts, except 

 in so far as it varies with the remiges. These latter will be seen to vary 

 from 33 to 44, and as the first row of upper-coverts is always in numerical 

 agreement, some correlating influence between the remiges and coverts 

 must necessarily be present. 



Fig. 3, Outer surface of wing showing more clearly the arrangement of the rows of 

 feathers. South African ostrich with two complete rows of upper-coverts and several 

 shorter rows, all continued round the elbow. 



The second row of upper-coverts on the other hand is in a marked 

 degenerative phase, the losses taking place for the most part at its distal 

 end, in contrast to the proximal end of the first row of under-coverts. 

 The full normal number necessary for complete alternation with the first 

 row of coverts is not often present (Fig. 3) ; sometimes six or seven, or 

 even as many as ten, are missing, but all intermediate numbers are to 

 be found (Fig. 4). Occasionally one or two of the feathers in front of the 



4. Wing of North African ostrich with extreme reduction of feathers (cf. Fig. 3). 

 The first row of upper-coverts with only 35 plumes has five less than the marginal 

 row, and the second row is still further reduced, as well as the number of smaller 

 rows. The wing as a whole is narrower than that from which Fig. 3 was drawn, and 

 the plumes are not continued round the elbow. 



