256 The Unity of the Organism 



finally able to get its mouth into contact with its prey. 

 Then the victim, itself but little smaller than the nemertean, 

 disappeared down the latter's "throat" with almost the 

 rapidity with which the lash was retracted into and thrust 

 out of its pouch. How much of this highly complex per- 

 formance, so eminently useful to the nemertean, was purelv 

 reflex, how much chemotactic, and how much instinctive { 

 And who will assert positively that there was no trace of 

 consciousness, even of intelligence, in it? 



An extremely interesting line of inquiry is suggested by 

 cases of "trial and error" like this where at one extreme the 

 "errors" are not much less numerous than the successes, and, 

 at the other extreme, are cases in which the errors are re- 

 duced almost to nil. A type case of this last would be the 

 poise-and-spring of a cat after its prey. With little doubt 

 a closely graded series could be made out running through 

 from one extreme to the other. A cardinal interest in the 

 inquiry would be as to the extent to which the simple reflex, 

 tropistic reflex, instinct, and intelligence figure in the dif- 

 ferent grades. Would it not turn out that the gradual 

 diminution of error through the series would be, generally 

 speaking, concomitant with the increase of intelligence? I 

 suspect so. 



Tendency of Subrational Activities to Excessiveness 



The fourth and last certainty about reflex and instinc- 

 tive activities to receive attention is their tendency to ex- 

 cessiveness their way of going beyond what is necessary or 

 even really safe for the welfare of the organism. Although 

 from several points of view this is one of the most impor- 

 tant aspects of the whole subject, it has received surpris- 

 ingly little attention, especially by the modern school of ex- 

 perimental zoology. 



Probably every one who has observed animals widely and 



