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 10x8x6 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 bj^ 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 
inactivity, 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 having 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 away 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(1, 1906, 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. 
