176 TOR KEY. 



TEXT-FIGURE 2. 



A, 32, forming 36 cells, formation of the fourth quartet ; B, 36-cell stage from 

 the side, 4^ or M, ccelomesoblast cell ; C, same stage from lower pole ; D, 24, 

 forming 32 cells from the upper pole ; E, 36, forming 40 cells, formation of apical 

 rosette. 



