244 REPORT OF COMMISSIONERS OF INLAND FISHERIES. 



These resulting reactions in the case of the early fovirth stage 

 lobster may offer an explanation of the fact that this stage is so 

 frequently caught in tow-nets drawn over the surafce of any of our 

 shore waters, while it has been a very unusual occurrence to secure 

 in this manner either the earlier or the later stages. The same causes 

 may also account for the reported facts that certain stages of the free- 

 swimming larvae of other forms of Crustacea are found more frequently 

 at the surface than are other larval stages of the same species, for it 

 altogether probable that the presence of organisms in bright sunlight 

 at the surface of the water may be indicative not of a positive photo- 

 tactic or heliotropic reaction alone, but also of a positive photopathic 

 response to the greater intensity of light in the surface waters. 



It was a noteworthy fact, however, that old fourth stage lobsters 

 would never manifest phototropic reactions with the same degree of 

 certainty as those demonstrated in the case of younger fourth stage 

 lobsters. Indeed, in a number of instances, fourth stage individuals 

 which were due to molt within a period of one or two days mani- 

 fested on black backgrounds a definite tendency towards a negative 

 reaction. The negative photopathic response was assumed without 

 exception after the lobsters had molted into the fifth stage, and this 

 reaction was then manifested with any combination of light intensity, 

 • color, or background, except red and blue lights on a black back- 

 ground, in which case the resulting reactions were often either con- 

 tradictory or obscure. The following tables show the reactions in the 

 case of the late fourth and the fifth stage lobsters: 



Experiment VIII. 



Conditions: Black Background (Similar Results Were Seldom 



Obtained on a White Background) ; Sunlight Bright; 



20 Late Fourth Stage Lobsters. 



Test. Light end Mid area. Dark end. Cover. 



1 9 4 7 



2 11 5 4 Reversed. 



3 7 6 7 



4 9 3 8 



