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. 168. — EMBRYONIC Area OF a Rahbit ok (? Nine) Days, with the Placental Area Partly Torn off. 



pr.a, Pro-amnion. a. a, Amniotic area, a.z\ Area vasculosa. a.pl, Area placentalis. ;■./, Sinus terminalis. — 



(After van Beneden ami Jul in.) 



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, />, 



proa !p 



FlG. 169. — Longitudinal Section of a Young Chick EMBRYO. 

 //. Head. Vd, Anterior portion of digestive canal (Vorderdarm). met. Mesoderm, fo, Fovea cardiacs. /•, 



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



I'i imitive 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 



