98 W. H. TALIAFERRO 
2. Reactions to light in specimens with one eye and the posterior 
half of the other eye removed. In the preceding section it was 
concluded that there are two localized sensory regions in the 
eye. If this is true, the animal should lose the reaction which 
| 
L 
Fig. 13 Drawing representing the shape of the pigment-cup of the right eye 
and indicating the location of the localized sensory regions. Arrow indicates 
longitudinal axis; A, anterior; P, posterior. Illumination of those rhabdomes 
which lie in the posterior part of the eye, R, or on the ventral lip, R’, resultsin 
the animal’s turning toward the side containing the eye, viz., the right. Illumi- 
nation of the rhabdomes which lie in any other part of the pigment cup, L, re- 
sults in the animal’s turning in the opposite direction, viz., away from the side 
containing the eye or the left. 
is supposed to result from the stimulation of either of these re- 
gions if it is removed. It was found, by very careful manipula- 
tion, that the posterior half of an eye could be removed leaving 
the anterior half uninjured—or at least, functional. After such 
operations each animal was allowed approximately twenty-four 
