REACTIONS TO LIGHT IN PLANARIA MACULATA 79 
Pearl (’03, p. 580) as a result of continued strong mechanical 
stimulation. He believes that ‘‘It indicates the effect of the 
organism as a whole on its reflexes.”” Boring (’12) has observed 
similar reactions in Planaria torva after continued directive 
illumination. He (p. 241) believes that— 
It is quite conceivable that the abrupt reversal of directions for 
brief periods, the ‘wild jumps,’ are forms of a compensatory movement, 
which acts as a relief, not for the continued stimulation, but for the con- 
tinued movement away from the stimulus. . . . . Itis quite possible 
that these muscles (i.e., the ones which steer the animal to one side) 
after the continued contraction involved in prolonged movement to 
one side, become cramped, and there follows what is probably a natural 
physiological codrdination, when the muscles on the other side contract 
suddenly and strongly, stretching the fatigued muscles. 
Both of the investigators quoted above observed the bending of 
the animal first toward and then away from the stimulated side 
only after long-continued stimulation. While this reaction cer- 
tainly does follow long-continued stimulation, I am not certain, 
judging from the results of numerous observations, that it is 
necessarily preceded by continued stimulation. When an animal 
is very strongly illuminated this reaction will follow immediately 
even though the animal has been previously subjected to very 
little photic stimulation. Such reactions unquestionably occur 
in earthworms and fly larvae immediately after stimulation. It 
is hoped that this matter can be taken up later in more detail. 
It would raise some interesting questions if short strong stimula- 
tion produced the same effect as long-continued weak stimulation. 
FUNCTION OF THE EYES 
A. Reactions to light in specimens with both eyes removed 
The majority of investigators who have worked on the question 
of the function of the eyes in planarians have reached the con- 
clusion that these organs play very little part in the character 
of the responses to light. Thus, as previously stated, Loeb 
(94), Hesse (97), and Parker and Burnett (’00) maintain that 
decapitated planarians react essentially the same as normal 
specimens, but that all reactions require considerably more time. 
