Rate of Regeneration in Cassio/^ea xainacluina. 



Table 5. Sl^ccifii rate of regeneration from each stiiinl^ of six removed arms on 



the same individual. 



With such remarkable variations existing within the same individual 

 in the regeneration rates of its arms, it is dangerous to draw conchisions 

 from the differences shown in rate of regeneration among the individuals 

 of a small series. As pointed out above, the variations in rate between pairs 

 of similarly injured individuals in table 2 are as great as the differences in 

 rate between two individuals which have suffered different degrees of 

 injury. It must be recognized, finally, that in these medusae the individual 

 variation in regeneration rates is sufficient to conceal a minor variation 

 which might be due to the degree of injury, did such exist. 



These tables giving the specific amount of regeneration from the arm- 

 bases of the same individual serve, at least, to indicate that no deductions 

 can be made from table 2 regarding the specific amounts of regeneration 

 from medusae injured to greater or less degrees. Tables 3, 4, and 5 indi- 

 cate still further that unless the differences in regeneration rates among 

 animals injured to greater and less degrees are constant and marked they 

 may verj^ likely be accidental, or else due to the peculiar responses of that 

 given form upon which the experiment was conducted. It is of interest 

 to note that Scott's ( 1907) study of regeneration in the fish's fin and the 

 present data from the medusae both indicate that the extent of injury is 

 negative in its influence on the rate of regeneration. Zeleny and Emmel's 

 results on animals that must molt in order that the regenerating bud may 

 continue to grow are due, I believe, to the influence of the regenerating 

 tissue on the molting cycle. 



