Feb., 1907.] 
Notes on a Sandusky Bay Shrimp. 
77 
At about 10:30 A. M. it was taken into the dark room, the light 
or open end being covered with a pasteboard cap having a V- 
shaped aperture 3-4 inch at the broad end and running to a point 
in 2 1-2 inches. In a few minutes (five or six), on hasty inspec¬ 
tion, the shrimps were found to be scattered among the vegeta¬ 
tion. White light shed through the aperture caused four or 
five shrimps to swim quickly to the light, others following in 
quick succession. Darkening the water again caused the shrimps 
to disperse. Red light, violet, blue, orange, indigo, green, and 
vellow, tried in above succession had a similar effect, i. e.. there 
was a more or less immediate response. There seemed to be a 
possible preference for red, which the writer has not been able 
to decide definitely. Colored light caused the shrimps to remain 
in the field of light better; this is probably due to the greater 
diffusion of the white light causing a broader and probably less 
definite field. The shrimps were in the dark room about two 
and a half hours, and during this time those nearest the light 
kept up a continual bumping against the glass. From sixteen to 
twenty shrimps were near the light with from four to twelve 
bumping the glass within the small area of light. Some seemed 
to rest on the sand at the bottom, while others kept up the bump¬ 
ing and vice versa. 
Taking the aquarium so that sunlight might pass through 
the aperture now reduced to 3-4 by 3-4 inches, there was no re¬ 
sponse. The shrimps gradually went back to the pond-weeds or 
adhered to the sides of the aquarium, with none near the light. 
At 7:30 P. M., of the same day (Aug. 2(i) the light experiments 
were again repeated, and the shrimps were found scattered 
throughout the aquarium, clinging principally to the pond-weeds. 
In two minutes with ordinary lamplight, twenty out of twenty- 
four (two of the twenty-six had died) were at the open end. 
Passing the acetylene gas light around the aquarium the shrimps 
followed it, with only a very faint light showing through the 
covered sides, making a complete circuit several times. 
Using the 3-4 by 3-4 inch aperture again with red, violet, 
green, blue, orange, and yellow light, practically the same re¬ 
sults were secured as above. A rest was given between the use 
of each color, during which time the shrimps invariably retreated 
to the pond-weeds. On flashing the light there was an immediate 
movement toward it, some individuals responding, however, 
more slowly. Each individual swam to and fro with head 
touching the glass. Several times it was observed that those 
which had gone too far into the dark corners, returned to the 
pond-weeds, but again came back to the light after coming once 
more in its wake, following a path as indicated by the arrows in 
the following figure. 
