EXPLANATION OF PLATES. 



PLATE I. 



Fig. I. Part of the cornea of the dragon-fly (lyibelhila) mounted flat 

 to show images, x 55. 



Fig. 2. Images formed by the corneules of the compound eye of 

 IfibeHula. 



Fig. 3. Section through part of the eye of I^ibellula showing crystal- 

 line cones and part of the pigment. Much of the pigment 

 was washed away in making the preparation, x 50. 



Fig. 4. Cornea and cones of the eye of a moth. The color of the pig- 

 ment is red. The cones are firmly attached to the corneules. 

 X 125. 



Fig. 5. Upper view of detached cones from the eye of a moth. The 

 pigment color appears to be diffused through the cones, x 125. 



PLATE II. 



Fig. 6. Group of ocelli of the wood louse (Oniscus or Porcellio) . x 45. 



Fig. 7. Part of cornea of eye of bee showing stiff hairs between the 

 facets. X 250. 



Fig. 8. Eye of grasshopper. Section showing cornea, cones, rhab- 

 doms, ganglionic cells and tracheae, x 35. 



Fig. 9. Fragment of cornea of common house-fly (Musca). Some of 

 the facets are quadrangular and some are hexagonal. The red 

 pigment appears nearly black in the photograph, x 60. 



Fig. 10. Section through the eye of katydid. The cones are concealed 

 by the pigment which is retained in situ owing to the thick- 

 ness of the section, x 25. 



