380 



THE BIOLOGY OF HYDRA : 1961 



Fig. 4. Regression of Campanularia hydranth. (Taken from time lapse 

 sequence). Note thickening of tentacles prior to resorption. Entire sequence 

 takes about 6 hours. 



dead animal is passed l^ack into the colony from whence it came, 

 and all that is left as a reminder of the former inhabitant is the 

 empty hydrotheca. 



What is the mechanism of cell death underlying these changes? 

 Is it similar to that which has been postulated or shown in other 



