1D W. H. TALIAFERRO 
GENERAL SUMMARY 
1. The eye of Planaria maculata is a typical turbellarian eye, 
consisting of two types of cells—the accessory cells forming the 
pigment-cup and the sensory cells or retinulae. 
_ 2. Each retinula consists of three regions—the nucleus-bearing 
region, the middle region, and the rhabdome, which show a 
striking resemblance to the three regions of the veretebrate 
retinula, viz., the myoid, the ellipsoid, and the rhabdome. 
3. Planaria maculata is negative to light and orients accurately 
to a horizontal beam of light. 
4, Orientation is, under certain conditions, direct; the animals 
may turn directly away from the source of light without pre- 
liminary trial movements. Trial movements are, however, at 
times functional in the process of orientation. 
5. The location of the bending of the body, when the head is 
turned away from the light, depends upon the intensity of the 
light—the higher the intensity of illumination, the more posteri- 
orly the point of bending is located. It is, however, never 
located farther back than the pharynx. 
6. If the intensity is high enough (or possibly continued long 
enough) to cause the bending to take place in the region of the 
pharynx, the animal no longer bends directly away from the 
light, but first toward and then away. 
7. During the reactions of animals to a horizontal beam of 
light, two marked motor reflexes occur, viz., the twisting reflex 
and the wandering reflex. These reflexes are defined on pages 
74 and 75. 
8. Specimens with both eyes removed do not orient in directive 
illumination as do normal specimens. They move, however, in 
general, away from the light. 
9. Removal of both eyes does not appreciably affect the rate 
of locomotion in either directive or non-directive illumination. 
10. Removal of the anterior end, on the contrary, greatly 
retards the rate of locomotion in both directive and non-directive 
illumination. j 
11. Specimens with one eye removed show no indication of 
circus movements or other abnormal motor activities. 
