96 Puget Sound Marine Sta. Pub. . Vol. 1, No. 11 



Experiment on Metabolism in Light and Darkness 



More light was thrown upon the influence of activity on metabolism 

 by an experiment made on fishes taken from each trough January 12. At 

 this time the ventral slits had not closed over the yolk-sacs in either group, 

 so that conditions from the standpoint of nutrition would be about the 

 same for both groups. Twelve fish of uniform size were picked from 

 the light trough and placed in a flask which contained 1230 cc. of water 

 taken from the pipe that supplied water to the troughs. A rubber cork 

 was inserted tightly leaving practically no air space in the neck of the 

 flask. The fish were placed in this flask at 10:17 P. M., and three minutes 

 later 12 fish of similar size were taken from the dark trough and placed 

 in a flask containing the same amount of water from the same source. 

 This flask was corked in the same way as the other. During the entire 

 experiment the temperature of the water in either flask did not vary one 

 degree from 7°C. The two flasks were placed just outside a window, the 

 first one being left in the light while the second was placed in a box from 

 which all light was excluded. The window faced the south so that the 

 direct light of the sun fell on the flask in the open during the day ; while 

 during the night a thirty-two candle power electric light, mounted in a 

 cup-shaped reflector and placed about two feet from this flask, threw a 

 strong light upon the fish. No disturbing influence other than the oc- 

 casional presence of the observer entered into the experiment, and the 

 fish being used to daily care were indifferent to the observer's movements. 



The flasks containing the fish were placed outside the window at 

 10:35 P. M. and were under observation for nearly an hour. During this 

 time the fish in the light continued to swim about vigorously in the lower 

 strata of water. Several observations were made of those in the dark 

 during this hour and they were found every time to be lying at the bot- 

 tom of the flask with scarcely any movement. Even if brought into the 

 light those fish accustomed to the dark did not become active like those 

 kept all the time in the light. At first they darted about but soon settled 

 down to the bottom in a state of inactivity. 



At 9 A. M. the next day 12 more fish from the light trough were 

 placed in an open flask of similar size and filled with water. This flask 

 was placed in the light beside the first one. These were to be used as a 

 control. The fish that had been in the light all night were at this time 

 swimimng about with great activity and kept up a darting movement 

 from the lower to the higher levels of the water and then back again, 

 occasionally seeking air at the surface of the water in the neck of the 

 flask. They exhibited a considerable degree of restlessness not observable 

 in those of the control. Their respiratory movements were 60 to the 



