Fig. 8o. — Secondary modifications of gastrula of Dendraster with 40 hr. of exposure to 

 Li CI m/60 from beginning of gastrulation; apical region secondarily elongated, entoderm 

 inhibited (from Child, 1938). 



Fig. 81. — Lesser degrees of secondary modification in Arbacia limited to apical region with 

 continuous exposure to various agents (from Child, igi()d). 



