DEVELOPMENT OF THE OPOSSUM 



51 



Fig. 6 Sections through the embryonic area of bhistocysts at the stage of 

 entoderm formation (X 90). .4, No.' 144 (1) d; B, No. 40 (2); C, No. 40 (3); 

 D, No. 40 (4); E. No. 40 (1); F No. 43 (9); G, No. 43 (7); H, No. 43 (8). ALB, 

 albumen; CG, coagulum; EMB.A, embryonic area; TR, extra-embryonic area; 

 SM, shell membrane. The albumen is seen to be absorbed more rapidly over 

 the embryonic area. In A and E, the shell membrane is misshapen and a large 

 space is left between it and the albumen layer. 



