100 
EYES AND SIGHT. 
insects into three types, and to those having true 
crystalline cones like the eyes of the bee he has 
given the name of eucofie eyes. 
Below the cones come the rhahdia (Figs. 45, 46, 
rb)^ which consist of delicate chi- 
tinous rods, having round them 
and united together throughout 
their length the eight retinulce.^ 
r, about which are placed pig- 
ment cells, which have a greater 
density at the upper, middle, and 
lower portions of the rods (Fig. 
44, P‘^)- The rods perfo- 
rate the basilar membrane (Fig. 
44, ;//), between which and the 
brain there are three ganglionic 
swellings, which Dr. Hickson (67) 
has called opticon ip), epiopticon 
St 
rl) 
Fig". 45. — Longitudinal Fig. 46. — Cross Section of Fig. 45 
Section of Part of Eye. through r. 
(e 0), 2J\d periopiicon (/> 0.) The periopticon is situated 
immediately behind the basilar membrane, and is 
separated from the epiopticon by a bundle of long 
