COMPLEX KES-PONSES 169 



influence upon its subsequent responses. This feature 

 in actinian reactions is a special application of a prin- 

 ciple that has long been familiar to physiologists. When 

 an explanation of it is sought, one naturally turns, as in 

 the case of the dying away of feeding responses, to ex- 

 haustion. Does not the initial stimulus, the vibration 

 from the first drop of water, so exhaust the neuromus- 

 cular 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 Kino- 

 shita (1911), who has shown by the use of several kinds 

 of weak stimuli that the responses to these fall off so 

 rapidly that it is highly improbable that exhaustion plays 

 any important part in the whole operation. Much more 

 likely is it that the neuromuscular apparatus through its 

 first response is brought into a state that is to be de- 

 scribed as one of inhibition rather than of exhaustion. 

 From this standpoint the condition left by the first stim- 

 ulus and response is not unlike that seen in the refrac- 

 tory period of nerve and muscle. At least it is clear that 

 the first response of the actinian has a relatively pro- 

 found influence on the subsequent reactions of this ani- 

 mal and that this influence lasts long enough five or 

 ten minutes to affect the outcome of later stimulation. 

 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 



