98 
CHAPTER XVI. 
EYES AND SIGHT. 
Compotmd Eye — Coritea — Hexagonal Facets — Ojn77iateu7u — 
Cry st aline Cone — Rhabdia — Retinulce — Pigment — Basilar 
Membra^ie — Opticon^ Epiopticon^ and Pei'iopticon — Crossing 
Nerve Fibrils — Number of Facets — Droiies' Eyes Laiger — 
Mosaic Vision — Microscopic Experimefit — Ste7U7nata^ or 
Ocelli — Dista7ice See7i — Use of Ocelli — Dro7ies 'luith White 
Eyes. 
The organs of sight consist of a pair of large com- 
pound eyes (Fig. 6, d) and the simple eyes, or ocelli 
(Fig. 6, i). 
If one of the compound eyes be examined under 
the microscope, we shall find the outer layer divided 
into a number of hexagonal facets, which are convex, 
and form the cornea. Between most of the facets are 
found long straight hairs (Fig. 44, //), which act as 
protection to the eye similar to eye-lashes, and they 
are also sensory. 
Every eye of insects is made up of several parts, 
each set of parts being called by Carriere (21) and 
Hickson (67) onimateutn., or ommatidiiun. 
Dr. Grenacher (57), who has described the com- 
pound eye of the bee in his admirable monograph, 
gives illustrations, which we have copied in Figs. 45 
and 46, and which, with Fig. 44, taken from Lowne 
(99, 100), will assist us in understanding better the 
structure of this organ. 
Each facet of the cornea (Figs. 44 and 45, is a 
