306 BIOLOGICAL LECTURES. 



as we have endeavored clearly to distinguish between instinct 

 as congenital and habit as acquired, we must not lose sight of the 

 fact that there is much interaction between instinct and habit, so 

 that the first exhibition of a deferred instinct may well be carried out 

 in close and inextricable association with the habits which, at the 

 period of life in question, have already been acquired. 



Although Mr. Morgan's young moor hen had undoubtedly 

 learned far more by experience before its first dive than my 

 young Nectunis could have learned before its first effort to 

 capture food, we are nevertheless well admonished to keep in 

 mind the fact that the activity here considered may not be pure 

 instinct. Allowing for the small though important part played 

 by intelligence, there remains a purposive sequence of coordi- 

 nated acts, which are always performed in essentially the same 

 manner by young and old, and by the young without instruction 

 or example or previous experience of like motive and stimulus. 

 In so far, then, as intelligence cannot possibly be a regulating 

 factor we must refer the activity to organization. 



4. Pause before the Bait. In order to exclude as much as 

 possible the influence of experience it will be well to confine 

 attention to the least variable part of the behavior. The con- 

 cluding phase of the performance is so typical and character- 

 istic, and so far removed from anything previously experienced, 

 that it may be regarded as a very near approach to pure instinct. 

 I have in mind the pause before the bait and then the qtdck 

 side-movement of the head as the jaws are opened to seize. 



If this series of acts represents an organic sequence, and if 

 the behavior as a whole takes the form determined by the 

 organization, as seems to me beyond reasonable doubt, we 

 have an instinct the history of which may be coextensive with 

 the evolution of the animal. We stand at the end of an inter- 

 minable vista. The specific peculiarities of organization in 

 Necturus form but an infinitesimal element of the problem. 

 Scarcely a feature of the instinct belongs exclusively to Nectu- 

 rus. It is at least widely diffused among vertebrates, especially 

 among fishes. The differences in the manner of execution 

 among different forms, so far as I have observed, are of quite 

 a superficial nature. The instinct evidently has its root in the 



