ANATOMY AND PHYSIOLOGY Tote) 
While the lateral ocelli are comparatively simple in structure, 
consisting of a small number of cells, the dorsal ocelli almost 
rival the compound eyes in complexity. 
Dorsal Ocelli.—These consist (Fig. 139) of (1) lens, (2) 
vitreous body, (3) retina, 
(4) nerve fibers, (5) pig- 
mented hypodermis cells, 
and (6) accessory cells, be- 
FIG. 139. 
tween the retinal cells and 
the nerve fibers. The lens, 
usually biconvex in form, is 
a local thickening of the 
general cuticula; it 1s sup- 
plemented in its function by 
the vitreous body, consist- 
ing of a layer of transpar- 
ent hypodermis cells; these 
in many insects are elon- 
gate, constituting a vitreous 
layer of rather more im- 
portance than the one rep- 
TI Median ocellus of honey bee, Apis mel- 
1e lifera, in sagittal section. h, hypodermis; 
resented in Fig. 139. 
retina consists ot cells more 1, lens; n, nerve; p, iris pigment; 7, retinal 
cells; v, vitreous body.—After REDIKORZEW. 
, 
or less spindle-shaped and 
associated in pairs or in groups of two or three, each group 
being termed a retinula. The basal end of each retinal cell is 
continuous with a nerve fiber (Fig. 140), according to Redi- 
korzew and others, and in some instances (Caloptery«) a nerve 
fiber enters the cell. Each retinula contains a longitudinal rod, 
or rhabdom, in the secretion of which all the cells of the retinula 
are concerned. Between the retinal cells and nerve fibers are 
indifferent, or accessory cells. Pigment granules, usually black, 
are contained in these cells, also in the retinal cells and around 
the lens, in the last instance forming the zvs. 
Vision by Ocelli.—Though the ocellus is constructed on 
