REPORT (^F COMMISSIONERS OF INLAND FISHERIES. 185 



influence of the light rays, and to learn which reaction was more 

 instrumental in determining the final reaction of the larvae. (4) The 

 last piece of apparatus to be mentioned was a rectangular glass 

 box 6 by 3 by 2 inches. This was used especially in studying the 

 mechanics of reaction in the case of isolated individuals. For illu- 

 mination, daylight (reduced to varying intensities by graded wedge 

 screens of colored gelatin, or colored glass plates) was used in most 

 of the experiments. In some cases, how^ever, acetylene lanterns 

 were employed, or, in a few instances, a brilliant oil burner. 



Experiments involving the use of the various pieces of apparatus 

 mentioned above were performed wdth young lobsters in the first 

 five stages. Instead of finding a uniform and constant type of 

 reaction for all stages and all individuals, it appeared that the 

 reactions underwent a great modification, not only from stage to 

 stage, but even during a single stage-period. It will not be attempted 

 here to describe in detail all the reactions of the larval lobsters. We 

 shall mention only the general results of a long series of experiments, 

 and attempt to present a clear view of the changes in reaction to 

 light which accompany the metamorphosis of the lobster as it passes 

 on from stage to stage. 



First Larval Stage. 



When the photopathic and phototactic reactions of the first-stage 

 larvse were first tested, they were both found to be positive; that is 

 to say, the first-stage larva appeared both to "choose" the lights of 

 greater intensity, and to move in the direction of the light rays (in 

 .case of the phototactic reaction) toward their source. No phase of 

 their behavior could be more striking than the definiteness of these 

 two forms of reaction to light. And it may be said here that in no 

 period in the later life of the larvse is there manifested a type of 

 response so universally invariable as the reaction given by the first- 

 stage larvse within the first few hours after hatching. 



This universal positive response, both to the intensity and to the 



