REACTIONS TO LIGHT IN PLANARIA MACULATA 99 
hours to recover. After each experiment the specimen was fixed 
and sectioned. In the majority of cases reconstructions were 
made of the portion of the eye that remained in the animal. As 
would be expected from the delicate nature of these operations, 
a great number of animals were discarded because of some injury, 
either to the portion of the eye which remained in the animal 
or to the surrounding tissues. In order to complete eight suc- 
cessful experiments, approximately fifty animals were operated on. 
As previously stated, an animal with one eye removed when 
illuminated directly from in front or slightly from the blind 
side turns toward the stimulated side. It was concluded that 
this reaction is due to the stimulation of the rhabdomes covering 
the posterior-median section of the eye-cup. Now, if this con- 
clusion is correct, the removal of the posterior region of the eye- 
cup should cause the animal to lose this reaction when illuminated 
from directly in front. 
The reactions of eight individuals with the left eye and the 
posterior half of the right eye removed were studied when illumi- 
nated with a horizontal beam coming from directly in front. In 
all of these the reactions were essentially as follows: The animal 
generally moved from 1 to 5 mm. directly toward the light at a 
greatly retarded rate, then it began to wander either to the right 
or left (fig. 14, 4). Observations indicate that such specimens 
turned toward the side containing the eye as often as from it. 
If the animal turned toward the side possessing part of an eye 
(in this case the right side), it eventually proceeded in an irregular 
course away from the light (fig. 14, D). There was never any 
evidence of orientation. If, however, the animal turned toward 
the ‘blind’ side (in this case the left side), the animal exhibited 
no marked reaction until the rays of light illuminated the eye 
laterally. When this took place the specimen oriented by turn- 
ing directly from the light until it was fairly accurately oriented 
(fig. 14, B). It then proceeded in a fairly direct course until a 
‘wandering reflex’ carried it out of the path of orientation. 
If the reactions of such an animal are compared with those of 
a specimen possessing the entire right eye, we see at once that 
there is a marked contrast. If the latter is illuminated from 
