LIGHT AND LOCOMOTION IN PHACUS AND EUGLENA. 205 



the lower intensity. When the intensity was increased there was 

 ordinarily no shock-reaction, and the organisms were timed im- 

 mediately after the intensity was changed, i.e., shortly after the 

 close of the test in the lower intensity. But when it was de- 

 creased there usually was a shock-reaction, and if this occurred, 

 the reading was not started until after the organisms had fully 

 recovered which usually required only a few moments. The in- 

 tervals preceding the readings in the lower intensities were, how- 

 ever, always somewhat longer than those preceding the readings 

 in the higher intensities. 



The results obtained are presented in Tables I. and II. Table 



TABLE I. 



RELATION BETWEEN INTENSITY OF LIGHT AND RATE OF LOCOMOTION IN Phacus 

 pleuronectes ( POSITIVE INDIVIDUALS). 



Each line contains two readings for one individual in different inten- 

 sities of light ; the last line, the averages for all 20 individuals. The record 

 in the lower intensity was obtained first in each instance. 



Time, in seconds, re- Time, in seconds re- 

 quired to travel .34 quired to travel .34 



Designation of mm. in an intensity mm. in an intensity 



individuals. of 1023 m.c. of 4128 m.c. 



1 5-7 6.2 



2 54 5-8 



3 6.7 7.4 



4 5-5 5-2 



5 6.4 7.0 



6 7-0 7-5 



7 6.2 6.2 



8 7-0 7-2 



9 4-9 44 



10 6.0 5.7 



11 5-5 54 



12 54 5-3 



13 54 5-3 



M 5-o 4-7 



15 5-2 5-2 



16 4.8 4.8 



17 5-0 5-2 



18 4-7 4-9 



19 t 5-2 5-0 



20 5-7 5-5 



Average 5.63 5.69 



