1886.] i Entomology. . 285 
of ganglion-cells which fails only at its posterior part. The gan- 
glion-cells are polygonal or roundish, varying in size ; they have 
a horny nucleus, and become stained whilst the medullary part 
remains clear. 
The compound eyes are well described by Viallanes (Ann. des 
Sci. Naturelles, 1882) for Musca. In Psyllidz they are somewhat 
simpler, having (1) at the surface numerous separate lenses of the 
cornea, slightly biconvex, (2) below them a layer of crystalline 
cones, often brownish, (3) next comes a dark layer of rhabdites 
forming the retina; each rhabdite being a slender truncated cone, 
narrowing inwards. The whole sys- 
tem of rhabdites converges towards 
not be clearly recognized in Psylli- 
dæ. The retinal fibers pass by the 
nA 
Tas 
Fig. 3. 
tance. The fibers passing this way toward the median brain- | 
mass form an “ outer decussation” (ed). Some fibers from this 
i 
decussation go to the adjoining cortex, some to the outer part of | 
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ig so. eek een 
S EA = 
