JT IG 57. SURFACE VIEW OF AN EMBRYO OF 52 HOURS. (After 

 Duval.) 



Aom, vitelline artery. C, heart. FO, olfactory pit. LC, lateral limits of 

 body. AT, tail. ^ 2 , mid-brain. Vva and Vvp, antenor and posterior branches 

 of the vitelline vein. Vo, eye. 



175 



