Hadley, Behavior of the Auiericau Lobster. 239 



larvae (Case i), while on the thirteenth and fourteenth days, as 

 the moulting-period to the fourth stage approached, the negative 

 reaction was less easily determined (Cases 3 and 4). It was 

 observed furthermore, that these larvae continued to manifest a 

 very definite positive photopathic response (Case 5), and that this 

 was maintained until the end of the stage-period. 



General conclusions on the behavior of larva; of the first three 

 stages — ^As the larvae, after the very definite positive photopathic 

 and phototactic reactions characteristic of the first part of the first 

 larval stage, pass on through the first stage-period, lights of low 

 intensity (red, orange, twilight, etc.), gradually lose their efficiency 

 in bringing about a positive phototactic reaction, while, on the 

 other hand, lights of a greater intensity (green, blue, daylight, 

 etc.) determine, more and more easily, a negative response. This 

 negative phototactic response, which may enter on the third day 

 of the first stage-period, changes again to positive as the first-stage 

 larvae draw near the first moulting-period. At this time, the lights 

 of low intensity are again effective in bringing about a positive 

 reaction, which is maintained until the larvae have moulted into 

 the second stage. 



While the photopathic reaction of newly moulted second-stage 

 larvae remains positive, the phototactic response is more often 

 negative, and this negative response is commonly maintained until 

 toward the end of the second stage-period. At this time, as was 

 observed in the first stage-period, a positive reaction again becomes 

 manifest as the larvae approach the period of moulting into the 

 third stage. 



While the positive photopathic reaction still obtains, the newly 

 moulted third-stage larvae commonly manifest a negative photo- 

 tactic reaction, and this, as was the case with the second-stage 

 larvae, is retained until the moulting-period into the fourth stage 

 approaches. At this time the reaction again becomes positive, 

 and continues so until the larvae have entered the fourth stage. 

 These general points in the behavior may be illustrated by the 

 following diagram (Fig. 6). 



The foregoing facts serve to emphasize further the statement 

 made on an earlier page, that we can not justly say that the larvae 

 of Homarus are positive to light or negative to light, or that they 

 react in this way to intensity, and in that way to the directive 

 influence of the light rays. But these observations do show that 



