84 W. H. TALIAFERRO 
As it is very improbable that the anterior end of a planarian 
can be illuminated without allowing a certain amount of light 
to enter the eyes, Walter’s experiments were repeated, using, 
however, specimens the eyes of which had been carefully cut 
out, and a horizontal beam of light instead of the localized point 
as in the above experiments. It was found that if a beam of 
light was thrown !aterally on the anterior end of such a worm, 
it turned away from the source of light in the majority of cases. 
It is important to notice, however, that this turning was not 
nearly so definite or precise as in the case of animals with eyes. 
A given specimen very often turned toward the light, swerving 
all the way around and thus proceeded away from the source 
of stimulation. The turning of such eyeless specimens was much 
more indefinite if the entire animal was illuminated instead of 
the anterior end. 
As the anterior end is more sensitive to light than the posterior, 
the animal would most likely maintain a position in regard to 
the light source such that the posterior end would shade the more 
sensitive anterior end. Such a position would tend to keep the 
animal directed away from the light and would explain the 
slight tendency to orientation observed in such specimens. It 
must not be supposed, however, that all of the reactions of speci- 
mens without eyes can be ascribed to this differential sensitivity 
of the anterior and posterior regions because a decapitated worm 
still proceeds, in general, away from the light. Although this 
is true, a decapitated worm does not show the slight tendency 
toward orientation such as is found in animals with both eyes 
removed. 
2. Rate of locomotion. As pointed out above, no difference in 
the rate of locomotion can be observed under ordinary conditions 
between normal specimens and those which have had both eyes 
removed. In order to test this accurately, however, the follow- 
ing experiments were devised, using both directive and non-di- 
rective illumination. The non-directive illumination was fur- 
nished by placing a 125-watt gas-filled lamp 30 c.m. above a 
circular aquarium in which the animals were moving. The di- 
rective light was furnished by the same apparatus used to test 
