38 C. H. TURNER. 



the movements. The checker-board pattern made it easy to 

 watch the movements of the animals. 



Using a scale of one-eighth of an inch equals an inch sheets 

 of cross section paper were cut to resemble the board, and the 

 tips of radii labeled in the same manner as on the board. These 

 were carried to the field in a loose-leaf cover. 



FIG. i. Checkerboard Plate. 



At the beginning of a series of experiments the board is placed 

 on the ground and adjusted until it is perfectly horizontal. If 

 necessary, it is screened from the sun. One of the sheets is 

 then numbered to correspond with the specimen to be investi- 

 gated. On the reverse side is recorded the position of the sun, 

 the position of the water and the direction in which the animal's 

 head is to be placed. In describing these positions the labeled 

 tips of the radii are used as reference points. The animal is 

 then placed in the center of the board with its head in the de- 

 sired direction and its movements traced on the cross-section 

 paper. When the animal reaches the edge of the board, it is 

 returned to its original position. This is repeated until it has 

 reached the edge of the board five times. It is then replaced in 

 the water a short time and then returned to the center of the 

 board with its head facing a new position. It is allowed to make 

 five trips in that case; these are recorded on a new sheet. This 



