136 



THE DEVELOPMEiNT OF THE CHICK 



J)ienc. 

 Mesenc. f y,i^f^_ 



Telene 



Cr.Fl. 



Mete/ic 



My el end. 

 9U.P 



Mye/enc.2 

 3. a 



S.5. 



S.io 



5.15. -^^(^ 



szoMm^^ 



pr.3tr 



Fig. 73. — Entire embryo of 20 s, viewed 

 as a transparent object from above. 

 The cranial flexure and the rotation of 

 the head of the embryo have made 

 considerable progress. 

 A. o. m., Omphalo-mesenteric artery. 

 Or. Fl., Cranial flexure. D. C, Duct of 

 Cuvier. Dienc, Diencephalon. Mesenc, 

 Mesencephalon. Metenc, Metencepha- 

 lon. Myelenc. 1, and 2, Anterior and 

 posterior divisions of the myeloncepha- 

 lon. Telene, Telencephalon. Vel. tr., 

 Velum transversum. Other abbrevia- 

 tions as before, x 30. 



cent to and surrounding the embryo, and a choriogenous zone, 

 comprising the remainder. 



The method of formation of amnion and chorion is as follows: 



