254 MILDRED HOGE RICHARDS AND ESTHER Y. FURROW. 



PLATE I. 



FIG. i. Section through the head of a normal fly. X 180 (16 mm. obj. 12.5 

 ocular). 



FIG. 2. Longitudinal section through several ommatidia of a normal fly (1.9 



obj.). 



FIG. 3. Cross section of a single ommatidium of a normal fly near the distal end 

 of the rhabdomeres. X 1500 (2 mm. obj., 12.5 ocular). 



FIG. 4. Cross section of a single ommatidium of a normal fly more proximal 

 than that of Fig. 3 (same magnification as that of Fig. 3.)- 



FIG. 5. Details of the outer ganglia (Transverse section of head) . X 825 (1.9 

 obj.. 7.5 ocular). 



