Jenkinson, Germinal Layers of Vertebrates. 



The movement of the dorsal hp just described is due 

 to its growth over the surface of the egg, the axis of 



Fig. I. 



A — D. Views of the vegetative hemisphere of the Frog's egg during the 

 overgrowth of the blastopiiric lip. 



j5', F. Views of the lower surface during rotation of the whole egg. 



In all the figures the dorsal lip is on the upper side. In D the ventral 

 lip is just formed. 



(Original.) 



which has up to the present retained its original vertical 

 position. At this moment, however, the whole q^^ begins 



