MORPHOLOGY OF ANIMALS 



Fig. 1. Cleavage, Blastula and Gasirula of an Echinoderm (Eckinarachniiij). A, 2 cells; B, 

 4 cells ; C, 8 cells ; D, i6 cells ; E, 32 cells ; F, Optical Section of a Blastula of about 128 

 cells showing a hollow sphere. The cavity in the sphere is the blastocoel. G, H, I, optical 

 sections of young, medium and old gastrulae ; a, anus; be, blastocoel; bp, blastopore; c, 

 coelom ; g, gastrocoel ; m, mouth ; me, mesothelium ; ms, mesenchyme. 



