AN EXPERIMENTAL STUDY OF THE RATE OF REGENERATION IN 

 CASSIOPEA XAMACHANA (BIGELOW). 



By Charles R. Stockard. 



INTRODUCTION. 



The suggestion has been advanced by Zeleny (1903 and 1905) that the 

 greater the degree of injury, up to a certain limit, the more rapid will be 

 the rate of regeneration. Zeleny 's studies were based on the regeneration 

 of the limbs in Crustacea and the arms of the brittle-star, Ophioglypha. He 

 was unable to offer any satisfactory explanation of why the regeneration 

 rate increased with the amount of injury, but advanced several suggestive 

 hypotheses which are subject to experimental test. First, he pointed out 

 that the animal with the greater number of appendages removed might 

 exercise the regenerating ones more vigorously than does the animal with 

 the smaller number removed. In other words, activity should increase the 

 rate of regeneration in animals. Child (1904) had also been led to think 

 that some regulating influence was exerted over regenerating tissue by 

 movement and nerve impulses in the flat-worm, Leptoplana. I have suc- 

 ceeded in devising two different ways of testing the influence of rest and 

 activity on the regenerating tissues of the medusa and find no increase in 

 the rate of regeneration to result from activity. 



It was also suggested that the amount of available food might regulate the 

 rate of regeneration. Those crayfish most injured have more food to draw 

 from, since the other appendages are not present to take their share of it. 

 Morgan (1906) has subjected this question to thorough investigation and 

 finds that the amount or rate of differentiation of the regenerating organ is 

 independent of the food supply, although the size of the organ is greater 

 in well-fed individuals than in starved ones. " So long as there is enough 

 food material in the blood or other fluids of the body to allow growth to take 

 place at all it goes on at a rate determined by the peculiarities of each level, 

 and largely independent of the food supply." Here Morgan mentions one 

 of the most interesting points connected with this subject — that is, the in- 

 fluence of different levels of the body, or of an organ, on the rate of regen- 

 eration. In the fish's caudal fin it was found that new tissues regenerated 

 faster the nearer the cut was to the base of the fin, and slower the nearer 



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