1905.] NATURAL SCIENCES OF PHILADELPHIA. 157 



EXPLANATION OF PLATES VI, VII, VIII. 



PLATE VI, Fig. 1. Section of entire eye and optic lobes. The heavy lines show 

 the course of the nerve fibres as worked out by Kenyon (diagram- 

 matic) . 



PLATE VII, Fig. 2. Ommatidium of young pupa before rhabdome is differenti- 

 ated and at time of first pigmentation of retinula cells. 



Fig. 3. Ommatidium of older pupa, showing differentiation of rhabdome 

 and lens formation. 



Fig. 4. Cross-section through distal end of cone of pupa of same age as 

 fig. 2, showing corneal pigment cells. 



Fig. 5. Cross-section through cone of older pupa. 



Fig. 6. Cross-section through proximal end of cone of pupa (same stage 

 as figs. 3 and 5). 



Fig. 7. Cross-section through cone of young pupa. 



Fig. 8. Cross-section through retinula of young pupa before rhabdome 

 formation. 



Fig. 9. Cross-section through distal end of retinula of young pupa, show- 

 ing first traces of pigment. 



PLATE VIII, Fig. 10. Entire ommatidium (somewhat diagrammatic). Adult. 



Fig. 11. Entire ommatidium, as if dissected out, without outer pigment 

 cells (diagrammatic). Adult. 



Fig. 12. Section of entire ommatidium, showing distribution of pigment. 

 Adult. 



Fig. 13. Cross-section just proximal to lens, slightly oblique. 



Fig. 14. Cross-section through extreme distal ends of retinulse and proxi- 

 mal ends of cones, slightly oblique. 



Fig. 15. Cross-section through retinulae, showing relation of outer pigment 

 cells in this region. 



Fig. 16. Cross-section through retinulse in region of nuclei. 



Fig. 17. Cross-section through retinulse in region of proximal nucleus. 



Fig. 18. Cross-section of eye, cutting basement membrane parallel. The 

 distinctness of nerve fibres of each ommatidium is shown. 



