212 



JOSEPHINE ALBERTA WILLIS. 



hundred animals exposed for varying periods. It is evident 

 from an examination of this table and from Fig. I, which shows 

 the same results graphically, that the rate of first movement per 

 minute exposure is apparently inversely proportional to the 

 length of time the animals are exposed. 



4 



100 

 minutes exposed 



.150 



FIG. i. Abscissa: The length of time in minutes the animal is kept under the 

 influence of pure COz. Ordinate: Rate in minutes per minute exposure to the 

 gas, of the first movement. (For further description see text.) 



From Table II. and Fig. i, it may also be seen that up to about 

 thirty minutes exposure to the gas the change in rate of the 

 first movement is rapid ; above this there is no perceptible change. 



It seems that the length of exposure to carbon dioxide, when 

 above one hour, has an effect on the time to the first movement. 

 Below this time limit, variations may be considered as due to 

 individual differences. Perhaps a thousand determinations 

 would be necessary to establish each point on a perfect curve. 

 However, individual differences vary within limits and the data 

 from the experiments performed are sufficient to determine the 

 trend of the curve, as is given in Fig. i. 



In order to determine the relation between the first movement 



