The Arthropod Eye. | 
863 
ramifications of the distal end of the optic nerve were not seen 
and have been inserted from Pat- 
ten. 
On the external surface of the 
compound eye is the facetted 
chitinous cornea, each facet of 
which is regarded as a lens (2). 
Immediately beneath this comes 
a layer of epidermal (hypoder- 
mal) cells, ¢, the existence of 
which was utterly ignored by 
Grenacher. These secrete the 
cornea. Next in order are some 
cells (retinophorze, r) which are 
rather complex in their structure 
and relations. There are four of 
these to each facet, and they lie 
exactly below the correspond- 
ng epidermal cells. The nuclei 
are placed in the outer ends, and 
thence the protoplasm runs back- 
Wards to the basal limit of the ret- 
inal portion of the eye marked by 
the line at in the figure. A short 
distance from the surface they 
contract to form a slender stalk 
or style (s), and these enlarge, in 
à graceful manner, to form a ped- 
Xcel (9), 
= y thin, and the space be- 
tween the four cells which make 
up one optic element, or ‘om- 
atidium,’ is occupied by a trans- 
Parent body, the crystalline cone 
). Below the cone the retin- 
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