VISION. 599 
spherical form of the lens, the anterior surface of which pro- 
jects far beyond the pupillary opening; the presence of a pro- 
Fic. 441.—Transverse section of the simple eye of a beetle larva (after Claus and Grenacher). 
CL, corneal lens; Gk, subjacent hypodermic cells (vitreous humor); P, pigment in periph- 
eral cells of latter ; Az, retinal cells ; St, cuticular rods of latter. 
cess of the choroid (processus falciformis); and usually the 
absence of eyelids, the cornea being covered with transparent 
skin. 
The eye of the bird, in some respects the most perfect visual 
NG) 
Xo 
in 
Fig. 442.—Diagrammatic horizontal section of eye of cuttle-fish (after Hensen and Gegenbaur). 
KK, Sechalle cartilages ; C, cornea; L, lens; ci, ciliary body of lens; Ri, internal layer 
of retina; Re, external layer of retina; P, pigment layer ; 0, optic nerve; go, ganglion ; 
k, papillary cartilage ; ik, cartilage of iris. 
