REACTIONS TO LIGHT IN PLANARIA MACULATA 85 
the reactions of specimens in a horizontal beam of light. In 
both cases the rate of locomotion was determined by means of 
a pantograph previously described in the section on methods. 
Ten normal specimens were placed in a dark room for twenty- 
four hours and then their rate of locomotion both in directive 
and non-directive illumination was ascertained. Throughout the 
experiment the animals were kept in the dark when not being 
observed, so as to keep the preliminary light environment as 
nearly constant as possible. After the rate of locomotion for 
the ten normal specimens had been ascertained, both eyes were 
TABLE 1 
The effect on the rate of locomotion of removing only the eyes as compared with the 
effect of removing the entire anterior end 
AVERAGE RATE OF 
LOCOMOTION IN 
MILLIMETERS 
PER SECOND NUMBER 
OF 
N TRIALS 
Directi SNOEE 
TeHi CEN 
men Norn Specimens.) oo. ss. Hse sas. see eet eek 1.18 Halal 40 
The same with both eyes removed: 
1) Two hours after removal of eyes............... 1.25 39 
2) Twenty-four hours after removal of eyes....... 1.10 1.08 55 
The same with anterior end removed: ‘ 
Twenty-four hours after operation................ 0.62 0.71 45 
removed from each specimen and, after twenty-iour hours, their 
rates of locomotion were again measured. In the case of non- 
directive illumination, the rate of locomotion was also obtained 
two hours after the removal of the eyes. Then, in order to see 
if the removal of the anterior end had the same effect as removing 
only the eyes, thesame specimens were decapitated, and after 
twenty-four hours their rates of locomotion were again ascertained. 
The results of these experiments are tabulated in table 1. 
This table shows that, in directive illumination, the average rate 
of locomotion for the ten normal specimens was 1.18 mm. per 
second; that after the eyes were removed, the rate in the same 
