Hadley, Behavior of the American Lobster. 297 



can be characterized as a "selection from among the conditions 

 produced by varied movements" (Jennings 1906b, p. 452). 

 Indeed there are no "varied movements" in the reactions by 

 which the body-orientation to Hght is brought about. The only 

 way in which the term "random movements" can, be apphed to 

 the orientation of the larval lobsters is in its relation to the variable 

 extent of the revolutions or rotations. It cannot be denied that 

 this degree may be dependent upon the physiological states of the 

 larvae (for instance, fatigue or freshness), but, after all, this point 

 is irrelevant to the present discussion, since it is the direction of 

 the immediate turning and not the extent of it, which is the impor- 

 tant consideration. 



The foregoing experiments throw but little light upon the ques- 

 tion of intensity of light versus direction of light. Indeed it is 

 probable that the latter phase of the problem is not of great impor- 

 tance except in cases where the light rays are effective by passing 

 through the body as in the case of the electric current, which, as the 

 writer has shown elsewhere (Hadley 1907a) causes reaction only 

 when the direction of the current holds a certain relation to the 

 longitudinal axis of the larvae. It is clear, however, that the direc- 

 tion of the light rays does modify the reactions of the larval in two 

 ways: (l) By determining which of the two eyes shall be most 

 stimulated, thus causing a body-orientation in which the longitu- 

 dinal body-axis is thrown into line with the direction of the light 

 rays, so that the eyes shall be equally stimulated; (2) by determin- 

 ing what parts of the surfaces of the tzvo eyes shall be stimulated 

 equally, and thus producing a body-orientation in which the pos- 

 terior lateral surface (Fig. 22, a.l.s.) of the eyes receives the 

 strongest stimulation, and the anterior lateral surface {pd.s.) the 

 least. These reactions, and the consequent progressive orienta- 

 tions of the larvae, the writer has called reactions to the directive 

 influence of the light. That there may be, in addition to these 

 responses, reactions to the intensity of light as Holmes (1901) 

 and others have considered possible, it is still permissible to believe, 

 and in the earlier pages of this paper the writer has pointed out 

 some reactions of larval lobsters, which, although not perfectly 

 understood, may be included under the head of photopathic 

 response. 



The foregoing experiments were carried on at the Experiment 

 Station of the Rhode Island Commission of Inland Fisheries at 



