104 



THE DEVELOPMENT OF THE CHICK 



a.c.s. 



op. Ves. 

 cep/i. Mes 



EG. 



V.o.m. 



3. a 



/}.T. 



3.Z 



//eh. 



pr. str. 



Fig. 59. — Embryo of 7 s from above drawn 



in balsam with transmitted light, x 30. 



a. c. s., Anterior cerebral suture, ceph. 

 Mes., Cephalic Mesoblast. F. G., Fore-gut. 

 N'ch., Notochord. n. T., Neural tube. op. 

 Ves., Optic vesicle. Pr'a., Proamnion. i)r. 

 str., Primitive streak, s 2, s 7, Second and 

 seventh somites. V. o. m., Omphalo-mes- 

 enteric vein. 



