3 l8 FERNANDUS PAYNE. 



aquarium placed on the solid earth, so no better nor more natural 

 conditions could have been found. At the university, the experi- 

 ments were made in a basement dark-room with black walls, 

 where the temperature remained practically constant. The 

 aquarium was set on a stone pedestal. 



Only very simple experiments were made and conclusions 

 have not been reached until after an examination of more than 

 one series of fishes, although the data of only one series will be 

 given. 



Apparatus. 



My apparatus consisted of an aquarium, a light screen, a heat 

 screen and a lamp. The aquarium was 18 inches long, 15 inches 

 high and 1 2 inches wide. The light screen was made of heavy 

 cardboard and was placed between the end of the aquarium and 

 the heat screen, so as to shut out all light except that entering 

 from one end of the aquarium. A small aquarium was used for 

 a heat screen. Its sides were of clear glass, parallel and placed 

 3 inches apart. This screen was placed 2 y^ inches from the end 

 of the aquarium. The water used in both the aquarium and 

 heat screen was filtered. Two lamps were used, one an acety- 

 lene lamp of one hundred candle power, and the other an arc 

 lamp of eight hundred candle power. 



Experiments and Observations. 

 My experiments at Mitchell were made with the hundred 

 candle power lamp. First, the lamp was placed 32 inches from 

 the end of the aquarium and with it in this position the whole 

 aquarium was lighted. As the aquarium was 18 inches in length 

 there was considerable difference in the intensity of the light at the 

 two ends. With ten fishes, ranging from 2^ to 4 inches in 

 length in the aquarium, counts were taken once a minute for 

 thirty minutes, and at the end of this time the counts showed 163 

 fishes in the end of less, and 137 in the end of greater intensity. 

 Before making this observation and with the aquarium lighted 

 just enough to enable me to see the fishes as white objects, I took 

 counts to see whether they showed any preference for one end of 

 the aquarium over the other. Thirty-five counts gave me 176 

 fishes in one end and 174 in the other. So the large number of 



