xii LIST OF ILLUSTRATIONS. 



FIGURE PAGE 



hy, hypoderm ; c, cuticle ; 6, anterior part of brain ; a, eye ; 



ne, nerve-fibrils ; c, anterior blood-vessel . . . . . . 13 



16. Diagrammatic section through a papilla of touch of Ouchidiura. 



a', a", two layers of the cuticle ; a, biconvex thickened portion 

 of the cuticle ; 6, enlarged epithelial cells ; 6', ordinary epithe- 

 lial cells ; c, cellular body ; c?, cells ; n, nerve . . . . 14 



17. Diagram of the structure of the soft and some of the hard parts 



in the tegmentum of a shell of a Chiton (^Acanthopleura spiniger), 

 as seen in a section vertical to the surface, and with the margin 

 of the shell bordering on the girdle lying in the direction of 

 the left side of the drawing. /, Calcareous cornea ; A, iris ; 

 g, lens ; k, pigmented capsule of eye ; n, optic nerve ; r, rods 

 of retina ; n', branches of the optic nerve, perforating the cap- 

 sule wall, and terminating in 6', 6', b', ocular sense-organs ; 

 p, p, nerves to sense-organ ; m, body of sense-organ cut across ; 

 a, p, fusiform body of sense-organ entire ; a, obconical termi- 

 nation of sense-organ ; e, nerve given off by one sense-organ 

 to another, b" . . . . . . . . . . . . . . 15 



18. Diagram of forms of hairs in insects, a, Ordinary surface hair ; 



6, plumose natatory hair ; c, hair of touch ; d, auditory hair ; 



e, olfoctory hair ; /, taste hair ; n, nerve hair . . . . 16 



19. Part of the proboscis of a fly (Musca). n, nerve ; g, ganglionic 



swellings; s, tactile hairs or rods ; c, cuticle . . . . . . 17 



20. Right half of eighth segment of the body of the larva of a gnat 



(jOorethra plumicornis). EG, Ganglion ; iV, nerve ; g, auditory 

 ganglion; gb, auditory ligament; Ch, aixditory rods ; a, auditory 

 nerve ; e, attachment of auditory organ to the skin ; 6, attach- 

 ment of auditory ligament ; hn, Jm', termination of skin-nerve ; 

 t6, plumose tactile hair; h, simple hair ; tg, ganglion of tactile 

 hair; ?m, longitudinal muscle ,. .. .. .. ..18 



21. Taste-buds of the rabbit, X 450 20 



22. a, Isolated taste-cells from the mouth of a rabbit ; b, two cover- 



cells and a taste-cell in their natural position, X 600 . . 20 



23. Termination of the nerves of taste in the frog, showing the 



ramifications of the nerve-fibres and their connections with the 

 cells of taste, X 600 21 



24. Inner layer of skin of the proboscis of Asterope Candida, X 400. 



a. Cuticle ; 6, terminal (nerve) organs ; c, ganglionic cells ; 



d, longitudinal muscle ; e, transverse muscle . . . . . . 22 



25. Taste-organ of the bee. B, Horny ridge ; R, JR, sensory pits ; 



C, C, skin of the mouth ; L, muscular fibres; A, A, muscular 

 fibres ; S, S', a b c d e f, section of the skin of oesophagus . . 26 



