148 JOSEPH KRAFKA, JR. 



PLATE II. 



FIG. 8. Cross-section of the head of a three-day pupa (seventh day). The 

 facets (F), pseudocone cells (P), rods or rhabdome (/?), and the basement 

 membrane are practically complete. Epc is the epiopticon. 300 X. 



FIG. 9. Enlarged outline drawing of two ommatidia in this stage. 1300 X. 



FIG. 10. Outline drawing of two ommatidia of the adult. The figures at 

 the side are cross-sections of an ommatidium at various levels. 1300 X. 



FIG. 11. Composite drawing of the head of a bar-eyed mutant (at the left) 

 and a full-eyed wild adult (at the right) to show the striking reduction in the 

 size of the optic tract in the former. 200 X. BO is the optic tract of the 

 mutant, O is that of the full-eyed wild stock. 



