REPORT OF COMMISSIONERS OF INLAND FISHERIES. 



213 



entered the horn, e. Thus, as in case B, the negatively reacting 

 larvae had merely grouped themselves in the horn where the light 

 was least bright. When the Y-tube was so placed that the arm, c, 

 overlay a sheet of white paper the result was different. The larvae 

 congregated in horn, b, which was, under these conditions, the region 

 of least light intensity. 



The four cases mentioned above were supplemented by other 

 experiments involving the use of colored glass plates, which were 

 placed over the horns of the Y-tube in such a manner as to create a 



Showing the ues of the Y-tubes. 



difference in the intensity of light in the two horns, as shown in 

 Fig. 1, E. F; or sometimes the light striking one horn would merely be 

 intercepted by interposing a red, orange, or yellow glass plate between 



