THE COMPOUND EYE OF INSECTS AND CEDSTACEA. 
29 
Fig. 8. Simple e}’e of Vespa crabra. Vertical section showing cornea 
and lens as above (a, b) } c, bacillar stratum j d, choroid pigment j 
e, retinal cells. 
Plate XXXVIII. 
9. Section of portion of eye of craj'-fish — Astacus fluviatilis: 
cornea ; b, bacillar stratum ; c, optic ganglion. 
„ 10. Sections across a bacillum at different points in its length (see 1, 
2, 3, 4, fig. 11); showing its four-lobed shape where it swells to 
form the “ crystalline body ; ” next in order, its cruciform shape 
in the middle ; its four-ribbed club-like expansion below ; and 
lastly, its simple round form where it pierces the pigment lying 
on the optic ganglion. 
„ 11. Shows in detail all the parts lying under a corneule in direct 
(radial) line to the optic ganglion. Astacus fluviatilis. a, 
corneal facet; slieath — on the inner wall are seen three 
nuclei adhering to it ; c, four-lobed enlargement (^^ crystalline 
body ”) continuous below with (d) the quadrangular nerve rod ; 
e, inner four-ribbed club-like swelling ; f, optic ganglion. 
„ 12. Shows the same details in eye of Herbstia condyliata ; a, b, c, d, 
e, f, as in former fig. ; four-lobed (nucleated) expansion of 
substance situate between the crystalline body (c) and club- 
shaped swelling below (e). 
„ 13. The same details in eye of Dynastes, letters as before. 
„ 14. Ditto ditto ditto Procrustes coriaceus ; a,b, c, d, e,f, g, 
as before ; j, fine tracheae lying inside the sheath. The red 
lines denote muscle fibrils within the sheath. 
„ 15. From eye of Mantis religiosa, letters as before. 
„ 16. Ditto Schizodactyla monstrosa, letters as before. 
„ 17. Ditto Syrphus; a, trachial tubes; b, c, d, e, as before. 
„ 18. Ditto Acridium coerulescens ; a, four-lobed crystalline body ; 
b, sheath— with pigment deposit ; c, nerve ; d, muscle fibril. 
