PLATE 2 



EXPLANATION OF FIGURES 



Differential inhibition. ■ 

 GAB Narrow-angled pluteus with somewhat inhibited oral lobe. 

 TAB Final stage with greater degree of differential inhibition. 

 8, 9 Differentially inhibited blastula and gastrula. 

 10, 11 Exogastrulation. 



12, 13 Final stages of more extreme differential inhibitions showing decrease 

 of angle of divergence of skeletal rods. 



14 Anenteric pluteus, probably from an exogastrula. 



15 Askeletal form. 



16 Spherical anaxiate form. 

 17, 18 Partial basal gastrulae. 



19 to 21 Final stages of small basal forms. 



22 Degeneration of enteron in spherical form. 



120 



