296 'Journal of Comparative Neurology and Psychology. 



ceases to influence the behavior of the larval lobsters. From this 

 moment on, a multitude of conditions appear to be brought to 

 bear to determine the consequent progressive orientation of the 

 young animals in one sense or the other. No longer can we say, 

 "same stimulus, same reaction" (Spaulding 1904), for there is 

 now no constant form of reaction even to the same stimulus. The 

 reactions appear to be no longer so dependent upon the nature of 

 the external stimulus, but are more largely regulated by the "phys- 

 iological states." This we might consider as the cumulative 

 result of a long series of previously acting stimuli, to which others 

 are constantly being added with two effects; first, of bringing about 

 a definite reaction determined by the nature of the stimulus and 

 by the present physiological state; second, of further modifying 

 the physiological state itself, so that even the reapplication of the 

 same stimulus might provoke a quite different reaction. It can 

 not be doubted that the series of changes, which occur in the behav- 

 ior of the lobster larvae as they pass through the successive stages, 

 is largely due to this gradual modification of the physiological 

 condition — the cumulative effect of a long series of antecedent 

 stimuli. 



We may sum up the preceding paragraphs by saying; (i) 

 The reactions by which the body-orientation of larval lobsters is 

 produced are invariable motor reflexes, and the method of such 

 orientation is, therefore, quite in accord with the requirements of 

 the local action theory of tropisms. (2) The reactions by which 

 the progressive orientation is produced, although appearing to be 

 simple reflexes, are not invariable but are dependent upon many 

 conditions of stimulation, and especially upon the physiological 

 states. 



In view of these facts, it appears that, while the body-orientation 

 of the larval lobsters is not of primary importance in determining 

 the index of the progressive response to the directive influence of 

 the light rays (since the body-orientation and the progressive 

 orientation are dependent upon quite different factors), still it is 

 of primary importance in determining the general line along which 

 the movement shall take place, either toward or from the source 

 of light. It is shown by these points that this type of response is 

 not in agreement with Jenning's theory (1906b), in which the 

 process of orientation is of secondary importance, for neither the 

 immediate nor the final body-orientation of lobster larvae to light 



