186 REPORT OF COMMISSIONERS OF INLAND FISHERIES. 



directive influence of the light rays, remained unchanged, under 

 nearly all degrees of illumination, for the first 24 to 36 hours of the 

 lobsters' existence. After this period of time, however, it was 

 usually observed that the first signs of a negative reaction began 

 to appear; and that, by the time the larvse were two daj's old, in 

 the majority of instances the negative phototactic reaction had 

 assumed prominence in determining the behavior of the first-stage 

 larvse. Even at this time, however, whether the reaction was posi- 

 tive or negative appeared to depend very largely upon the intensity 

 of the light to which the larvse were submitted. It very frequently 

 happened that larvae which gave a very definite positive reaction in 

 light of low intensity, would manifest just as definite a negative 

 reaction when the intensity of the light was augmented beyond a 

 certain point. The negative reaction to daylight was usually main- 

 tained by the first-stage larvae until the approach of the first molting- 

 period. 



At the approach of the molting period, which usually occurs on 

 the fourth or fifth daj' of the first stage-period, a return of the positive 

 reaction that had characterized the behavior of the larvse during the 

 first two days after hatching was observed. This positive reaction 

 began by a decreasing sensitiveness to lights of greater intensity, and 

 culminated, during the few hours before the molting, in a striking 

 positive reaction even to lights of great intensity. During this 

 change in the phototactic reaction, the photopathic reaction re- 

 mained invariably positive. 



To summarize the reactions of the first-stage larvae it may be said 

 that: (1) The photopathic reaction remained positive throughout the 

 stage. (2) The phototactic reaction of the larvae, aged about 1 

 days, was definitely positive; but after 2 days it changed to nega- 

 tive, only to return to the positive reaction as the molting period 

 with the second stage approached. (3) The phototactic reaction of 

 first-stage larvse invariably overcame the photopathic reaction, and 

 although any phototactic reaction requires a certain optimum 

 intensity of light, the general behavior of the first-stage larvae is 



