actinian behavior 221 



Jennings to have insisted on its importance. When an expla- 

 nation of this phenomenon is sought, one naturally turns, as in 

 the case of the dying away of feeding responses, to exhaustion. 

 Does not the initial stimulus, the vibration from the first drop 

 of water, so exhaust the neuromuscular mechanism that it is 

 incapable of receiving in an effective way a second stimulus till 

 after a certain time for recovery? 



This subject has been quantitatively studied by Kinoshita 

 ('11), who has shown by the use of several kinds of weak stimuli 

 that the response to the first stimulus is so considerable as com- 

 pared with that to most subsequent stimuli that it is highly 

 improbable that exhaustion plays any important part in the 

 whole operation. Much more likely is it that the neuromuscular 

 apparatus having responded once, assumes a state rather of 

 adaptation than exhaustion and thus saves the organism from 

 subsequent and useless responses. From this standpoint the 

 condition left by the first stimulus and response seems to be that 

 of inhibition — of the production of a refractory period so to 

 speak — rather than that of exhaustion. At least it is clear that 

 the first response has a relatively profound influence on the 

 organism and that this influence lasts long enough — five or ten 

 minutes — to affect subsequent stimuli. Here, then, in the truly 

 nervous activities of actinians is evidence of the beginning at 

 least of nervous states analogous to the more complex conditions 

 found in higher forms. 



In attempting to make clear the conditions under which the 

 second or modified response takes place, care must be exercised 

 that confusion does not arise as to the nature of the explanation. 

 To one class of workers, those having a physico-chemical bent, 

 a satisfactory explanation of the modified form of response 

 would be found in an understanding of the interaction of the 

 second stimulus and the receptor together with the chain of 

 events that terminate in the muscular movements. This form 

 of explanation is concerned exclusively with the working mechan- 

 ism as such and has nothing to do with its historical origin. The 

 second form of explanation, the one more likely to be adopted by 

 those of a more biological turn, would seek for an understanding 



