REPORT OF COMMISSIOXERS OF INLAND FISHERIES. 211 



the arrow. Immediately the larvae would orient themselves with 

 their heads toward the end, a, and pass through the tube toward 

 the light. As soon as they approached the region marked x, they 

 would come under the influence of the dark background bounding 

 the side of the tube. Immediately, as we have seen to be the case 

 in previous instances, the larvae would undergo a swing of the longi- 

 tudinal body axis so that the head would come to face more or 

 less obliquely the dark background. The directive influence of 

 the rays, however, continued to draw the larvae on, but since they 

 must travel in the direction in which the tail was directed, they 

 entered the horn of the tube, b, and continued until further progress 

 was prevented by their reaching the end of the horn. Space will not 

 be taken to show the numerical counts resulting from the actual 

 experiments. Suffice it to state that nearly all of the positively 

 reacting larvae, of whatever stage or age, when submitted to these 

 conditions of experiment, reacted as has been described above. 



This experiment was modified by so placing the Y-tube that the 

 horn, b, overlay a piece of black paper. The results were invariably 

 the same: the majority of larvie entered that horn of the tube 7iot 

 overlying the black background. 



Case 2. 



In this case the conditions of the experiments were further modi- 

 fied by so reversing the Y-tube that the horns pointed away from the 

 window. In this instance larvae which were manifesting a negative 

 reaction were employed, and were first placed in the end, a, nearer 

 the window. When the light was admitted, the larvae at once 

 oriented with their heads directed away from the light, and began a 

 progression away from the window. When they had reached the 

 point designated x, they immediately underwent a swing of the 

 longitudinal axis, as in previous cases, so that the head became 

 directed toward the black ground bounding the outer surface of the 

 horn, c. In this direction thev continued to advance until the 



