3io 



VICTOR E. SIlKLFOkM). 



Pool Animals. 



Notropis swain quickly aboul but spent most of its time- in 

 the medium and light I birds. 



The other two species of fish and Caloptery.v spent most of 

 their time in the darker third while the other species were not 

 active. 



2. METHODS OF SHOW TESTS AND TYPICAL RESULTS. 



The final tests or show experiments were made in a Yerkes 

 light grader such as is described by Mast ('n p. 61), (fig. 35). 

 A 132-watt Nernst lamp was used 50 cm. from the lens (with a 

 triangle of 70 mm. base and 82 mm. altitude) and the experimen- 

 tal box (5 cm. wide by 25 cm. long) was turned at an angle of 

 45 degrees to the direction of the light and with the nearest comer 

 at the focal point of the lens and at the left end of the gradient 

 field. A glass plate (G of Fig. 36) was placed across the corner 



DRAIN 



FIG. 37. Showing the relation of the hollow-walled glass-sided experimental 

 box. The water came from the supply pipe, passed through the coil which rested 

 in a vessel of water kept hot by a bunsen burner. The flow and gas were readily 

 adjusted to give any desired temperature within experimental needs. The water 

 passed from the coil to the hollow wall of the light box. It was necessary to empty 

 the box often and when this was done the flow was temporarily turned out through 

 the drain nearest the coil without changing the rate of flow. 



to prevent the animals from moving into the darkness. The 

 experimental box had glass sides and metal ends. All parts not 

 made from glass were .painted dead black and the light which 



