462 



ZOOLOGY FOR MEDICAL STUDENTS 



CHAP. XIV 



it will be noticed that it is situated not over the centre of the embryonic 

 body but towards its hind end — indicating that the growth of the amniotic 



V.C- 



ms. 



Fig. 194. 



Third-day Fowl embryo viewed as a transparent object, a.e, Edge of amnion ; am, amnion ; 

 E eye ; H, heart ; w.s, mesoderm segments ; oi, otocyst ; s, indications of pre-otic mesoderm 

 segments (?) ; v.a, vitelline artery ; v.c, visceral cleft II ; * portion of splanchnopleure bulging 

 downwards into the yolk, forming a recess in which lies the head of the embryo. 



fold does not take place at an equal rate all round. As a matter of 

 fact it first appears and grows most rapidly at the head end — forming a 

 hood which grows back- over the head region. The hinder and then the 



