392 



THE BIOLOGY OF HYDRA : 1961 



Fig. 17. Time lapse photographs of control (upper) and irradiated (lower^ 

 colonies of Campanularia — 1, 36, 72, 108, 144, and 180 hours after receiv- 

 ing 100,000 r. 



death in Campanularia and in hydra is probably quite similar to 

 that which occurs in humans. Second, it is evident that mortality is 

 an evolved character that may or may not express itself even in 

 closely related species. Why should one strain of hydrozoan be 



