REPORT OF COMMISSIONERS OF INLAND FISHERIES. 245 



From the above experiments it appears that we have the probable 

 explanation of the characteristic behavior of late fourth stage 

 lobsters; i. e., the tendency to seek the bottom and to hide under 

 shells, rocks, or grass. It further appears that there is no good 

 reason to attribute this manner of behavior, as do some writers, 

 either to a negative heliotropism (phototaxis) , or to contact irri- 

 tability. 



Experiment IX. 



Conditions: Black Background; Medium Sunlight; 

 12 Fifth Stage Lobsters. 



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



1 2 4 6 



2 2 3 7 



3 2 2 8 Reversed. 



4 13 8 



The results of these experiments may also explain, to a certain 

 degree, the facts which appear through the observation of large 

 numbers of the larval stages of Homerus when confined and exposed 

 to different light conditions, and also interpret to some extent the 

 behavior observed in the larval and early adolescent stages of lobsters 

 under natural conditions of environment. The first three larval 

 stages, when confined in the large twelve-foot white canvas bags 

 in which they were observed, manifested at all times a marked 

 tendency to sink toward the bottom — except perchance at night, 

 when more active swimming is observed in all the stages. This 

 tendency during the daytime could not be controlled in any way. 



It seems entirely possible that this reaction may be explained upon 

 the grounds of negative photopathy, for although it is certainly true 

 that the young lobsters below the fifth stage are under certain con- 

 ditions positively phototactic, still it may be that a certain intensity 

 and background is required for the fullest manifestation of this re- 

 sponse. For instance, at night, it was possible to evoke a seemingly 



