DOROTHY B. SPANGENBERG 



417 



Fig. 1. Migration of gastrodermal cells in grafted Chlorohydra treated 

 with lipoic acid. 



new tentacles in H. littoralis, it is our opinion that some cnido- 

 blasts migrate short distances to become incorporated into the 

 new tentacle; however, most of the nematocysts for the new ten- 

 tacles are formed after cutting from the differentiation of interstitial 

 cells during the early part of the regeneration period. Histological 

 sections of lipoic acid treated Hydra offered the best evidence of 

 interstitial cell migration. In these organisms, where maturation 

 of the interstitial cells is inhibited, large numbers of undifferent- 

 iated interstitial cells were seen at the pre-tentacle site twenty 

 hours after cutting, whereas only a few cnidoblasts containing 



