41 8 NATHAN FASTEN. 



EXPLANATION OF PLATE III. 



FIG. 4. Enlarged drawing of the tripartite eye observed in Fig. 3, to show 

 the details of structure. X 1,928. 



FIG. 5. Frontal section of the eye, shewing details of internal structure, and 

 also the optic nerve (o.n.). X 1,272. 



