PHYLOGENY OF THE PAL^OGNATH^ AND NEOGNATH^. 



159 



b. Pterylosis of the Embryo and Nestling. 



The ripe embryo and the nestling Rhea americana appear to differ from the adult 

 only in that the anterior portion of the apterion spinale is absent, and that there is a 

 distinct oil-gland. 



I find no trace of an " egg-tooth " in the ripe embryo, which I myself removed from 

 the egg. This is also wanting in the embryo Dromoeus and the nestling Casuarius. 

 Concerning Dromwus, however, see p. 154. The late Prof. Jeffery Parker failed to 

 find it in Apteryx at any stage of its growth. 



Steuthiosidj;. 



Struthio camelus. 



1 have not been fortunate enough to secure either nestling or adults of Struthio ; 

 consequently I am obliged to fall back upon the published accounts of others. Nearly 



Fig. 3. 



A. Lateral view of an embryo of Struthio, after Lindsay, to compare with Apteryx. Note the absence of a 



lateral cervical apterion. 

 B. Lateral view of an embryo of Apteryx australis, right side (after Parker), to show the pterylosis. INoto 



the distinct pteryla colli ventralis and dorsalis and the pteryla humeralis. 



all that can be gathered, moreover, concerning the pterylosis of the trunk of Struthio 

 concerns embryos only. The wing of the adult Ostrich has been ably described by 



2a2 



