10 



CORA D. REEVES 



a glass plate 20 cm. long, not shown in the figures, and enters at the top of the closed 

 end of compartment 2. The water flows in a thin sheet over the glass plate and 

 drops from it into the aquarium. This permits the escape of excess gases from the 

 water. When the plate is not used the fish develop symptoms of gas-bubble dis- 

 ease. From the plate the water drips into the aquarium at a rate somewhat above 

 one drop per second. Outflows are provided in the center of the ends of sub-com- 

 partments 1' and 1" at 17 cm. from the bottom. 



b. The Lamphonse. 



The larnphouse is a black rectangular wooden box 172 cm. long, with an internal 

 cross-section 22 cm. by 23 cm. A partition of thin tin divides it lengthwise into 

 two equal compartments. The inside of the lamphouse is blackened with several 

 coats of lamp black and shellac. The single glower Nernst lamp inside each half 

 of the house (A'' in fig. 2) is of the 0.6 ampere, 220 volt D. C. type. Openings, shown 

 opposite arrow-heads in fig. 4, at the bottom and at the top of the lamphouse, and 

 below L. H. m fig. 2, afford ventilation and prevent excessive heating. They are 

 hooded to prevent the escape of light. The lower end of the lamphouse rests on the 

 experiment aquarium, which is so placed that the partition C (figs. 1 and 2) is 

 beneath the partition MO (fig. 2) in the lamphouse. Thus two continuous, dark- 

 lined tunnels are formed with a white diffusing surface set at an angle of45° across the 

 bottom of each. A wooden frame {EG in fig. 2) rests on the top of the sub-compart- 

 ments V and 1" of the aquarium in the position of ejgh of fig. 1, and surrounds 

 the lower end of the lamphouse. 



FIG. 3 



Diagram of compartments /' and /" as seen from the center of the doorway of 

 partition A, figure 2, showing the lower end of the lamphouse with food-bar attached 

 to the frame upon which it rests. 



//, rj', food-bar. 



K, electro-magnet which holds // horizontal until released. 



S, S, stimulus plate. 



w, water level. 



c. Food-bar. 



At the center of the side gh of this frame is fastened a narrow metal strip or food- 

 bar. It is 0.8 cm. wide and 24 cm. long after being looped at its center to surround 



