THE DEVELOPMENT OF THE FROG 251 



not yet covered by the overgrowth of the pigmented cells. 



G. 



H. 



8- 



Fig. 58 



A to /. A series of views of the lower pole of the Frog's ovum, illustrating 

 the overgrowth of the white hemisphere by the pigmented cells and the 

 formation and changes of position of the blastopore. For full description 

 see text, dl, dorsal lip of blastopore ; bp, blastopore. The horizontal lines 

 mark the horizontal lines that are drawn through the lower pole of the 

 ovum, but in D, E, F they have inadvertently been placed too low down 

 in the figures. 



The dorsal lip has not only increased in size, but it has 



