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DISCUSSION 



Comfort: We have done some work on regeneration in guppies 

 (Comfort, A., and Doljanski, F. (1958). Gerontologia (Basel), 2, 266) 

 which might have some relevance to what you said about protein 

 utilization, Dr. Gerking. We cut off the tips of the tails and measured 

 the percentage restoration in length at various times. In female 

 guppies up to three years of age the growth curves were typically 

 asymptotic, and the corresponding curve for percentage restoration 

 of an excised regenerate was roughly a mirror image of them. In 

 fish that had been kept without much to eat, the growth curve 

 flattened out and the regeneration rate fell exactly as in freely 

 growing fish approaching full size. Full-size and retarded brood- 

 mates were therefore behaving in almost the same way as regards 

 regeneration. If retarded fish are then allowed to grow, the rate of 

 regeneration rises until growth declines again. In other words, as 

 the asymptote for size under given conditions is approached, the 



