Cofnpensafory Regulation. IJ 



whole on the regeneration of its arms as one of retardation, we 

 must take the values a^, b^, c^ and d ^ as representing most nearly 

 the original local stimulus effect. Then without changing the 

 values of r4 or R^ we may rearrange the formulae, making a^ = a^ — 

 r^, etc., and ai+b^+c^+di = a^ + b^+c^+d^-R^. 



The regeneration of the arms of Ophioglypha thus offers us a 

 very good example of the influence of conditions away from an 

 injured surface upon the regeneration at that surface. The 

 result may be stated in two ways and each mode of statement may 

 be made to lead to a separate mode of interpretation. 



We may say that the rate of regeneration increases with an 

 increase in the number of removed arms. With this statement as 

 a starting point it is natural to assume that, in the cases where 

 more than one arm is removed, the stimulus of the additional 

 operations or of the additional regenerating organs exerts an 

 accelerating influence upon the regenerating tissues at any one 

 such surface. 



Another mode of statement is the following: The increase in 

 the number of removed arms is necessarily accompanied by a 

 decrease in the number of uninjured arms present, and the rate 

 of regeneration of a removed arm therefore increases as the 

 number of uninjured arms still remaining decreases. If the 

 uninjured arms exert a retarding influence upon the regenerating 

 tissue at an injured surface we can understand why a removal of 

 additional arms may bring about an increase in rate of regenera- 

 tion of each. The discussion of this interpretation involves the 

 whole problem of nutrition and perhaps the whole general problem 

 of form regulation as well. It will be best to reserve further dis- 

 cussion until we have examined the other experiments to be 

 described in the following pages. 



But whether we consider the influence of the organism as a 

 whole to be one of acceleration or one of retardation, we must 

 recognize in either case that the regeneration rate is not a matter 

 which involves only the local conditions at the wounded surface as 

 determined by the direct action of the operation. It seems, on 

 the other hand, to be bound up with intricate reactions affect- 

 ing the whole character of the activities and organization of the 

 animal. 



