198 



PROCEEDINGS OF THE AMERICAN ACADEMY. 



a similar substance. Both ends may also be attained, to a certain extent, 

 by increasing or decreasing the angle of inclination of the plate. An 

 examination of the tables given by Davenport and Perkins ('97, p. 103) 

 shows that the largest average number of negative responses occurred 

 when the glass plate was vertical ; that is, when the mechanical diffi- 

 culties were greatest. There is a gradual decrease in this average 

 (and a corresponding increase in the average number of positive re- 

 sponses), as the angles of inclination of the plate with the horizon were 

 diminished from 90° to 60°, 45°, and 80° successively. At the still 

 smaller inclinations of 22^°, 15°, 7°, and 0° (i.e., horizontal), however, 

 there is on the whole an increase in the average number of negative 

 responses, though this is quite irregular. Since the proportion of anterior 

 to posterior region of the animals experimented on is not known, we 

 cannot tell how far this factor may have been the cause of this irregu- 

 larity in the sense of the response. 



I have made a few experiments by varying for the same individual the 

 angle of inclination of the plate. The animals were all in good condi- 

 tion throughout the experiments. The results — given in Table V. — 

 show a decided increase in negative geotaxis with increase in the angle 

 of inclination. 



TABLE V. 



Per Cent of Geotaxis at Different Angles of Inclination of the 



Support. 



The most striking case is the complete reversal of geotaxis, seen in the 

 first animal experimented on. 



