A. 



3' 



C. 



Diagram of Three Stages, A, B and C, in tlie Growtii of a 



Feather. 



1, horny layer of epidermis ; -', ■lerniinative layer of epidermis ; 3, dermis whieh forms 

 a papilla at 3i : 4, follicle eontaiuing feather ; 5, yonng feather : •'., blood-vessels. 



P.g. 



P.f. 



ect. 







ent. 



meso. 



Fig. 57 



Transverse Section through the Primitive Streak. 



ji.g.. primitive groove ; Ji.f., primitive fold ; eet., ectoderm ; ent., entoderm 



nieso., mesoderm. 



