212 REPORT OF COMMISSIONERS OF INLAND FISHERIES. 



majority of the larvse had gathered in this horn of the tube. In 

 this instance, however, instead of moving to either end of the horn, 

 the larvae frequently rested between x and c, 



Case 3. 



In this instance the black background bounding the outer side of 

 one horn was exchanged for a white ground of the same size, and 

 having the same position shown in Fig. C. In this case, third-stage 

 larvae giving a positive reaction were employed for the experiment, 

 and were started in the end of the tube, a. When the light was ad- 

 mitted, the usual body orientation resulted, and the larvae began their 

 progression through the tube toward the window. When they had 

 arrived at the point x, they would come under the influence of the 

 white ground and turn their heads away from this side. Progressive 

 orientation would continue and the larvae would eventually become 

 grouped in the horn of the tube marked c. Similar results w'ere 

 obtained when this arm of the tube was laid over a sheet of white 

 paper. 



Case 4. 



The previous experiment was further modified by reversing the 

 Y-tube so that the -horns were directed away from the window, 

 Fig. D. In this instance, larvae which were giving a negative 

 reaction were employed. They were placed in the end, a, and the 

 light was admitted. After the usual body orientation, the progres- 

 sion away from the window began to take place. When the larvae 

 reached the point x, and had come under the influence of the white 

 ground bounding the side of the tube, they would swing their heads 

 toward the left and continue their progress until all were gathered 

 in horn, c. This was somewhat unexpected. It eventually trans- 

 spired, however, that the white ground bordering the outer surface 

 of the tube did not act as a reflector or intensifier of the rays, but as 

 an opaque shield, cutting off the rays which would have otherwise 



