214 REPORT OF COMMISSIONERS OF IXLAXD FISHERIES. 



that horn and the source of iUiimination. In these cases the same 

 general results which we have seen in the four previous cases ap- 

 peared: The positively reacting larvae would gather in the horn where 

 the light intensity was greater, while the negatively reacting larvae 

 would group themselves in the horn where the light was less bright. 

 When one horn of the tube was covered with red glass, the other with 

 orange, the positively reacting larvae would gather in the orange 

 horn, while, if the experiment was modified for negatively reacting 

 larvae, they would congregate in the red horn. As a rule, larvae of 

 the earlier stage appeared to be more susceptible than the others to 

 slight differences in the intensity of light at the entrance to the 

 horns, and would react readily to such a slight difference of intensity 

 as that between red and "ruby" glass. (Unfortunately no means 

 of accurately measuring the entensities of light in which certain 

 reactions took place, was at hand.) Thus we have explained the 

 general tendency for positively reacting larvae to gather in regions 

 of greater light intensity; and, on the other hand, the tendency for 

 negatively reacting larvae to congregate in the regions of lesser light 

 intensitv. 



COXCLUSIOXS. 



It is not to be doubted that the types of reaction which have been 

 described in the previous pages are influential in determining, in a 

 large measure, the behavior of the lobsters under natural conditions 

 of environment. But when one attempts to interpret the daily 

 behavior of the larvae in terms of these tropisms, the results begin to 

 flavor of speculation. For instance, we know that under experi- 

 mental conditions the fourth-stage larva, when submitted to food 

 stimuli, will rise at once to the surface of the water and swim about 

 excitedly for some moments. We know also that the early fourth- 

 stage larvae, under experimental conditions, will leave a region of 

 low light intensity, and remain in a region of greater light intensity. 



