REACTIONS TO LIGHT IN PLANARIA MACULATA 87 
In regard to the rate of locomotion in specimens with both 
eyes removed, the disparity between the results of this paper and 
those of the former investigators undoubtedly lies in the fact 
that they drew conclusions regarding the effect of removing the 
eyes from the behavior of decapitated specimens. From the 
results given in this paper, it is evident that such conclusions 
are not valid, because removal of the anterior end itself, regard- 
less of the eyes, has a profound effect on the rate of locomotion. 
If the entire ventral surface of a planarian is functional as an 
organ of locomotion, a very simple explanation of the decrease 
of the rate in decapitated worms suggests itself. Removal of 
the anterior end would remove a part of the organ of locomotion 
and hence would undoubtedly decrease the rate of movement. 
It is very improbable, however, that this can explain such a 
great decrease. The general effect of the operation and possibly 
the loss of the ‘brain’ act upon the general physiological tone 
of the animal, causing locomotion, among other physiological 
activities, to be retarded. 
B. Reactions to light in specumens with one eye removed 
In regard to the reactions of planarians with one eye removed, 
Mast (710, p. 132), in a paper already referred to, makes the fol- 
lowing statement: 
Planaria with one eye removed, either by gouging it out or by cutting 
off one side of the anterior end obliquely, turn continuously from the 
wounded side for some time, evidently owing to the stimulation of the 
wound, since after this is healed they tend to turn in the opposite 
direction. After regeneration is nearly complete they orient practi- 
eally as accurately as normal specimens. 
Unfortunately, from the standpoint of the present investiga- 
tion, no note was made of just how far the eye itself was allowed 
to regenerate in such specimens before accurate orientation to 
light was observed. 
The present experiments were designed to ascertain how ac- 
curately specimens with one eye orient to the directive stimula- 
tion of light and to find out, if possible, the mechanism of this 
orientation. 
