REPORT OF COMMISSIONERS OF IXLAXD FISHERIES. 189 



tactic reaction, instead of changing to positive, became only the more 

 strongly negative. The photoj^athic reaction, on the other hand, 

 which, in the earlier stages, remained positive throughout, was found 

 in the fourth stage-period to undergo a change. While the early 

 fourth-stage lobsters manifested a positive phototactic reaction, this 

 gave place, during the advancing fourth stage-period, to a negative 

 reaction to the intensity of light. This reaction was invariably 

 manifested by the late fourth-stage larva:^. 



One other point of interest in the behavior of the fourth-stage 

 lobster may be noted in the relation between the phototactic and 

 photopathic reactions. We have observed in the earlier stages that 

 the phototactic reaction was dominant over the photopathic, and 

 was largely the controlling factor in determining the behavior. In 

 the fourth-stage lobsters the condition of affairs appeared to be 

 somewhat different. It was found that the photophatic reactions 

 had assumed a greater stability and were not so easily overcome by 

 the phototactic: and, as will be shown subsequently, the photo- 

 pathic reaction assumed a still greater importance in determining the 

 behavior of the fifth-stage lobster. 



Fifth-Stage Lobsters. 



The body form of this stage is very similar to that of the fourth- 

 stage larvae, and we might therefore expect similar types of reaction. 

 But we shall see that there are differences in behavior, and in this 

 case the points of difference are of such a nature that we can not attrib- 

 ute them either wholly or in part to changes in body form or in 

 the swimming appendages. But it is undoubtedly the consequence 

 of modifications in the body-processes of the lobsters themselves, 

 and may well be ascribed, perhaps, to changes that have resulted 

 from the cumulative stimulation during the earlier life of the lobsters. 

 Generally speaking, we may say that the reactions of the fifth-stage 

 lobsters were typical of the adult form, and were chiefly characterized 

 bv the light-shunning instinct. This form of behavior could be 



