xvm LIST OF ILLUSTEATIONS. 



EIG0EE ^^'^'' 



pigmented epithelium ; d, the lining epithelium of the mantle ; 

 e, the lens ; /, the ligament supporting the lens ; g, the 

 retina ; h, the tapetum ; k, the pigment ; m, the retinal 

 nerve ; n, complementary nerve , . . . • ■ • • ^^"^ 



98. Schematic representation of the soft and some of the hard parts 



in a shell of a Chiton (Acanthopleura), as seen in a section 

 vertical to the surface, and with the margin of the shell lying 

 in the direction of the left side of the drawing, a, Conical 

 termination of sense-organ ; 5, 6', ends of nerve ; c, nerve ; /, 

 calcareous cornea ; g, lens; h, iris; A, pigmented capsule of 

 eye ; m, body of sense-organ cut across ; n, nerve of eye ; p, 

 nerve of sense-organ ; /■, rods of retina .. .. .. l45 



99. Long section through the front (A) and hinder (5) dorsal eyes 



of Epeira diadema. A, Anterior eye ; B, posterior eye ; Hp, 

 hypoderm ; Ct, cuticle ; ct, boundary membrane ; M, muscular 

 fibres ; M, IT, cross sections of ditto ; St, rods ; Pg, P', pig- 

 ment cells ; i, lens ; (?4','vitreous body ; K, nuclei of the cells 

 of the retina; JTi, crystalline cones; St, retina; jVqp, optic nerve 147 



100. Section through the eye of a cockchafer (Melolontha). . .. 148 



101. Section through the eye of a fly. h.m, Basilar membrane ; c, 



cuticle ; e.op, epioptic ganglion ; n.c, nuclei ; n.c.s., nerve-cell 

 sheath; if./, decussating nerve-fibres; op, optic ganglion ; ^o, 

 pseudocone; pg, pigment cells; p.opj perioptic ganglion; r, re- 

 .tinula ; i2A, rhabdora; T, trachea; f.a, terminal anastomosis ; 

 Tty trachea; ti, tracheal vesicle ., ., .. .. 149 



102. Two separate elements of the faceted eye of a bee. J/, Cornea ; 



n, nucleus of Semper ; Kk, crystalline cone ; Fg, Fg'^, pigment 

 cells; i?^, retinula ; i2m, rhabdora ,, .. ., .. 150 



103. Eyelet of coclcroach. If, Cornea ; kk, crystalline cone ; pg', pig- 



ment cell ; W, retinula ; rm, rhabdom .. ., .. 152 



104. Eyelet of cockchafer. ?/, Cornea; M, crystalline cone ; pg,pg', 



pigment cells; r^, retinula; T'm, rhabdom ., .. ., 152 



105. Leptodora hyalina . . . . . . . . . , , . 155 



106. Eye of Mysis. n, Nuclei ; Zf, facets ; Kk, crystalline cones ; 



n', cells of the retinula; El, retinula; Fm, rhabdom; Cp, 

 blood-vessels; N, fibres of the optic nerve; M^^, N'^'^^, if^"^ 

 decussations of the fibres of the optic nerve ; G, G^, ganglia • 

 M, muscles for the movement of the eye-stalk ; JTtti, nuclei . . 157 



107. Coryca^us. a, h. The eye . . . . , . . , _ 153 



108. Eyes of Calanella Mediterranea. Fg, pigment cells ; N.fr, 



frontal nerves ; N.op, nervus opticus. The numbers show 



the numbers of the cells . . . . . . . . . . 159 



