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. 1 68. EMBRYONIC AREA OF A RABBIT OF (? NINE) DAYS, WITH THE PLACENTAL AREA PARTLY TORN OFF. 

 pr.a, Pro-amnion. a. a, Araniotic area, a.v, Area vasculosa. a. pi, Area placentalis. v.t, Sinus terniinalis. 



(After van Beneden and Julin.) 



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, p, 



proa 



FIG. 169. LONGITUDINAL SECTION OF A YOUNG CHICK EMBRYO. 



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

 Pericardial coelom. 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 



