100 W. H. TALIAFERRO 
directly in front, it turns sharply to the right, 1.e., toward the 
normal side. If, however, the posterior region of the right eye 
is removed, the animal no longer shows this reaction following 
such illumination. Instead, such specimens proceed in general 
Fig. 14 Diagram representing reactions of a specimen, possessing only the 
anterior half of the right eye, toa horizontal beam of light coming from directly in 
front. Arrows, beam of light; a, portion of eye remaining; b, portion of eye re- 
moved. If specimen turns to the left at A and assumes position B, it orients 
by followirg the path C. If, however, it turns to the right, it follows an indef- 
inite path, as, for example, D. EH represents the path the specimen would have 
followed had it possessed the entire right eye. 
for a short distance directly toward the light, and then turn either 
to the right or left. In other words, when observed under the 
effect of illumination from directly in front of the animal, removal 
of the posterior portion of the eye causes the animal to lose the 
reaction which ordinarily follows the illumination of this region. 
