4l6 NATHAN FASTEN. 



EXPLANATION OF PLATE II. 



FIG. 2. View of the eye as seen from the dorsal surface of the free-swimming 

 larva. The distribution of the pigment (p) is here seen to good advantage. The 

 facet-like surface of the ocelli may also be observed. X 1,760. 



FIG. 3. Cross-section of a larval organism through the region of the eye. The 

 position of the eye (e) is noticed to be between the brain (b) and the dorsal surface 

 of the body wall (w). X 460. 



