■65 



PLATE II. 



Figures 6-9 were drawn with a camera lucida, Bauseh and 

 Lomb microscope, ocular 10, objective 4. Plate reduced to two- 

 thirds in reproduction. 



Fig. 6. Longitudinal section of eye of 5 mm embryo. First 

 stage in the formation of the optic cup and the lens vesicle. 



Fig. 7. Longitudinal section of eye of 3.5 mm embryo, showing 

 primary optic vesicle. Note layer of mesenchyme between optic 

 vesicle and body ectoderm. 



Fig. 8. Detail of section of eye of 9 mm embryo. 



Fig. 9. Detail of longitudinal section of eye of 11 mm embryo, 

 showing general arrangement of vitreous fibers. 



