258 Proceedings of Indiana Academy of Science 
worms are photo positive only in very weak light, specimens with 
the brain removed are positive in strong light. 
The experiments referred to above also prove conclusively that 
the earthworm possesses cells which react to light, and that these cells 
are not limited in their distribution to the anterior end. In fact, ex- 
periments show that the worm is sensitive to light over its entire body, 
the anterior end being most sensitive, the posterior end next in sensi- 
tiveness and the middle region of the body least sensitive of all. 
These, and other experiments which were performed, seem to indi- 
cate that the Annelids as a group are negative in their reactions and 
orientations to ordinary light; that those forms which possess definite 
eyes seem to have the cells which function as photo-receptors localized 
in these eyes, while those worms that do not have perceptible eyes pos- 
sess cells which function as photo-receptors that may be distributed more 
or less over the entire body. Some of the annelids, at least, which are 
negative to ordinary illumination are positive to very weak light, and 
if the brain and the anterior photo-receptors are destroyed these worms 
also become positive to strong light. 
DePauw University. 
