258 MILDRED HOGE RICHARDS AND ESTHER V. FURROW. 



PLATE III. 

 Microphotographs. 



FIG. i. Side view of head of living normal fly. 



FIG. 2. Transverse section of head of normal fly, from slide loaned by Dr. F. 

 Payne. 



FIG. 3-7. Transverse sections of heads from eyeless stock. 



FIG. 3. Head is totally eyeless on left side, has very small eye on right. Section 

 does not go through optic tract of eyeless side. 



FIG. 4. Head has two small eyes. Section goes through optic tract of left side. 



FIG. 5. Head has slightly larger eye on right; is totally eyeless on left. Optic 

 tract of both sides in section. 



FIG. 6. Same as Fig. 3, but eye on right side is fairly large. 



FIG. 7. Head is totally eyeless on left, where section goes through the inner 

 ganglion, but misses the median. Right side has small eye. 



FIG. 8. Frontal section of head totally eyeless on both sides. 



