54 Jenkinson, Germinal Layers of Vertebrates. 



THE RELATION OF THE BLASTOPORE OF THE 

 AMNIOTA TO THAT OF THE ANAMNIA. 



The first serious attempt to get over the difficulty was 

 made by Balfour. Balfour held that the primitive groove 

 of the Amniota represented only the dorsal portion of the 



^ 2) 



Fig. 32. 



A. Diagram to illustrate Balfour's view of the relation of the primitive 

 groove of Amniota (d.b.l.) to the edge of the blastoderm or lip of the yolk 

 blastopore {y.b.l.). The two are connected by a posterior suture (the two 

 dotted lines) ; y. yolk. 



B — D. Diagrams to illustrate Rabl's view of the relaticn of the 

 Anamnian to the Amniote blastopore (after Keibel). 



B. Amphibian egg with closed blastopore and ventrally placed yolk- 

 mass ; the latter is bursting through the ventral body wall at x. 



C. Result of augmentation of the yolk. 



D. Protamniote condition reached by still further enlargement of the 

 yolk. The yolk is black in all three figures ; y.c. yolk cells. 



Anamnian blastopore {Fzg. 32, A, d. b. /.), the ventral 

 portion being found in the edge of the blastoderm {y. b. /.) ; 

 the two portions he supposed to have been originally 



