298 



STUDY OF YOUNG CHICK EMBRYOS. 



ward about the pro-amnion, pro.a, it has become free on all sides, and at ^the 

 same time the entodermal cavity has been carried forward with the head, 

 making the so-called fore-gut of English authors. This fore-gut is the anlage 



Fig. i68. — Embryonic Area of a Rabbit ok (? Nine) Days, with the Placental Area Partly Torn off. 

 pr.a, Pro-amnion. a. a, Amniotic area, a.v. Area vasculosa. a.pl, Area placentalis. v.t, Sinus terminalis. — 



[After van Beneden and Jiilin.) 



of the pharynx, the oesophagus, and the stomach. Underneath the posterior 

 portion of the fore-gut there has appeared in the mesoderm a coelomic cavity, />, 



praa 'p 



Fig. 169. — Longitudinal Section ok a Young Chick Embryo. 

 //", Head. Vd, Anterior portion of digestive canal (Vorderdarm). mes. Mesoderm, fo. Fovea cardiaca. /, 

 Pericardial ccelom. pro. a, Pro-amnion. Ach, Entodermal cavity, in life bounded below by the yolk. Pr.s, 

 Primitive streak. 



which serves as the connection across the median line with the amnio-cardiac 

 vesicles just described in surface views. We can, therefore, distinguish in 



