PV 



FIG. 47. SURFACE VIEW (DORSAL) OF AN EMBRYO OF 33 HOURS. 

 (After Duval.) 



A m, head-fold of amnion. C, heart. G jV, nerve ganglion. L M, medul- 

 lary fold. LP, mesoblast that will segment into mesoblastic somites. P P, primi- 

 tive streak. P V, mesoblastic somites. Sfi, sinus rhomboidalis. V2 and F3, 

 mid- and hind-brains. V A^ auditory pits. VO M, vitelline vein. 



140 



