A 



Fig. i6 



Fig. 15, A,B. — Harenactis attenuata. A, outline indicating levels of section, a-e of Table 2; 

 B, bipolar reconstitution from esophageal region; tentacles of disk at oral end develop more 

 rapidly and become longer than those of aboral disk (from Child, igoga, h). 



Fig. 16. — Outline of planarian indicating approximate levels at which fission can be in- 

 duced in long animals. 



