Feb., 1907.] Notes on a Sandusky Bay Shrimp. 77 



At about 10:30 A. M. it was taken into the dark room, the hght 

 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 sixj, 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 

 w'as 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 graduallv 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. 26) 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 acetvlene 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 w^th 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 slowlv. 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. 



