

PV 



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

 (After Duval.) 



Am, head-fold of a-nnion. C, heart. G N, nerve ganglion. L M, medul- 

 lary fold. L P, mesoblast that will segment into mesoblastic somites. />/", primi- 

 tive streak PK, mesoblastic somites. Sfi, sinus rhomboidalis. V2 and V3, 

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



140 



