76 The Ohio Naturalist. [Vol. VII, No. 4, 



the light. An Agrionid larva had been clinging to the glass in 

 front of the lamp for over fifteen minutes. (At this point the 

 lamp was taken away.) 



8:00 P. M. Examined again after the aquarium was in the 

 dark for two hours. The shrimps had changed their positions, 

 all but three or four having come to the surface of the water 

 at the margin. On flashing a red light into the water through 

 one end, two shrimps responded at once, the others did not change 

 their positions. 



(Note. — The aquarium used in the above experiment and the follow- 

 ing ones measured 10 x 8 x 6 inches. The sides were covered inside 

 with dense black cloth, ends open; a black focussing cloth served as a 

 cover for the top and one end. An acetylene gas lantern, of bicycle 

 pattern, was used for light, which in the above experiment was simply 

 shed in at the open end. A good red light was secured by screening the 

 face of the lantern with a cap of the best quality tissue paper. Far 

 better results were obtained in the following experiments by cutting 

 off all but a sharp well-defined path. When a full light is shed into the 

 water through the open end of the aquarium, there is a response to the 

 light, but because the water is lighted in comparatively so large an area, 

 the response is rather undecided.) 



During the following two days (Aug. 18-19) the aquarium 

 was kept in daylight, i. e., no experiments with artificial light 

 were performed. The shrimps were quite inactive, clinging to 

 the sides of the aquarium and seldom changing position. The 

 darker corners were evidently preferred during the day. This 

 was again apparent when the aquarium was covered with a fo- 

 cussing cloth and a path of sunlight was shed through an aper- 

 ture in a pasteboard cover placed over one end. 



Light experiments applied during the evening of the 19th 

 resulted in no marked or ready response to the stimulus, though 

 the light (artificial) was shed through a small aperture. This 

 inactivitv, I think, should be attributed to the fact that the 

 shrimps were in a pathological condition because of the condition 

 of the water, several clams ha\-ing already died in it. The 

 dragon-fly nymphs (four in number) on the other hand, darted 

 for the light immediately and remained there for the evening 

 excepting occasional excursions awav from the light, this but for 

 a moment, then to return and continue bumping against the 

 glass and swimming back and forth from side to side of the light 

 path. Several pond-snails also persisted in coming to the light 

 even after having been pushed aside repeatedly ; thigmotaxis, 

 however, eventually carried them straight up the glass and away 

 from the light. 



On Aug. 2(), H)()(), twenty-six shrimps were placed in the 

 aquarium after changing the water and other contents. There 

 was an immediate rush to the light end (daylight), which was re- 

 peated again and again on turning the aquarium end for end. 



