210 



EMBRY0L0GICAL TYPES 



on each side of the embryo, and soon covers over the latter 

 completely, much in the same manner as the neural folds 



■Pb. 



?«$* 







Fig. 98. — Gallus : embryo chick after 60 hours' incubation seen, A, from 

 the dorsal side by transmitted light, B, from the ventral side by reflected 

 light. (After Jenkinson.) 

 The head-end has turned and is lying on its left side ; the heart is twist- 

 ing ; the tail-fold has appeared, and the amniotic folds cover half the embryo, 

 a, auricular portion of the heart ; e, eye ; /, lens ; tf, tail-fold ; v, ventricular 

 portion of the heart ; vc, visceral cleft. Other letters as Figs. 91, 93, and 97. 



previously covered over the neural tube. The folds join 

 above the embryo, which now finds itself in a sac, the amniotic 



