446 'Journal of Comparative Neurology and Psychology. 



minutes. The mode of orientation has already been described. 

 In such a case the less illuminated side contracted. The animal 

 would be thrown around so that invariably, we may say, the other 

 side would be presented to the light. Once in a while, of course, 

 it might happen to get into the line of the rays, but the animal 

 is, so to speak, always becoming oriented, and never except acci- 

 dentally, for one resting interval, does it get into the line of the 

 rays. On account of its unsymmetrical movements it is of course 

 unable to take and keep such an oriented position (Fig. 5). 



Fig. 5. Diagram showing positive phototaxis in Corethra. L, source of light. 



The positive reaction changes gradually to negative rs will be 

 further shown in Experiment 6. Miall states that the animals 

 prefer the upper lighted waters, but preferably in a place shaded 

 somewhat by trees. The writer has collected them in great num- 

 bers from the surface waters of ponds at all seasons. In certain 

 Wisconsin lakes, the writer is informed by Mr. C. Juday, 

 Corethra larvae (species ?) go down in the daytime and come up 

 at night with great regularity and it is a very rare occurrence to 

 find Corethra near the surface in the daytime. The writer has 



