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CHAPTER VII.

The organs of vision in Insects and Crustacea-Ocelli—Compound

eyes - Cornea - Crystalline cones Retinula — Pigment-
Different forms of eyes-Structure of the optic lobes-Eyes

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CHAPTER XI.

On recognition among ants—Experiments with intoxicated ants

-Evidence against recognition by means of a sign or pass-
word-Experiments with ants removed from the nest as

LIST OF ILLUSTRATIONS.

FIGURE

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1. Diagram to illustrate possible origin of a sense-organ. c, Cuticle;

h, cellular or hypodermic layer 2. Diagram to illustrate possible origin of a sense-organ. C, Cuticle;

h, cellular or hypodermic layer 3. Diagram to illustrate possible origin of a sense-organ. c, Cuticle;

h, hypoderm ; n, nerve 4. Diagram of further stage in the origin of a sense-organ 5. Diagram illustrating a second possible origin of a sense-organ 6. Diagram of further stage in the origin of a sense-organ 7. Section through the simple eye of a young Dytiscus larva. h,

Hypoderm; l, lens; o, optic nerve; 9, P, modified hypodermic

cells; r, retina 8. Auditory vesicle of Ontochis 9. Pacinian corpuscle. a, Neurilemma; b, nerve-fibril; c, capsule;

d, peculiar fibres ; e, central cylinder 10. Papilla from the surface of the hand, X 350. a, Cone-like body;

b, nerve; C, end of nerve 11. Portion of the skin of the back of the hand. The centre figure

represents the arrangement of the hairs; CP, the cold-points;

WP, the warmth-points
12. Half a cross section through the brain and hinder pair of eyes of

Nereis cultrifera. 1, Hypoderm; 2, cuticle ; 3, retina; 4,
outer corneal cells; 5, inner corneal cells ; 6, brain; 8, 8a,
two places to which the brain sends large nerves, but where

the cuticle is unaltered ; g, gelatinous body
13. Part of upper nerve-ring and tactile epithelium of Lizzia. a,

Tactile epithelium ; g, ganglionic cell; nr?, upper nerve-ring 14. Diagram of part of the skin of a sea-anemone (Actinia). dz,

Glandular cell; nz, nervous cell 15. Anterior part of body of Bohemilla comata. 1b, Tactile hair;

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LIST OF ILLUSTRATIONS.

FIGURE

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hy, hypoderm ; C, cuticle; b, anterior part of brain ; a, eye;
ne, nerve-fibrils ; o, anterior blood-vessel

13 16. Diagrammatic section through a papilla of touch of Onchidium.

a', a", two layers of the cuticle; a, biconvex thickened portion
of the cuticle ; b, enlarged epithelial cells ; b', ordinary epithe-
lial cells; C, cellular body; d, 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. f, Calcareous cornea ; h, 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 b', 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, 5"

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

b, plumose natatory hair; c, hair of touch; d, auditory hair;
e, olfactory hair; f, 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 guat

(Corethra plumicornis). EG, Ganglion ; N, nerve; %, auditory
ganglion; gb, auditory ligament; Ch, auditory rods; a, auditory
nerve; e, attachment of auditory organ to the skin ; b, attach-
ment of auditory ligament; hn, hn', termination of skin-nerve;
tb, plumose tactile hair; h, simple hair ; ty, ganglion of tactile
hair; Im, 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 covercells 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 the proboscis of Asterope candida, X 400.

a, Cuticle; b, terminal (nerve) organs; C, ganglionic cells;

d, longitudinal muscle; e, transverse muscle 25. Taste-organ of the bee. B, Horny ridge; R, R, sensory pits;

C, C, skin of the mouth ; L, muscular fibres; A, A, muscular fibres ; S, S', ab c d e f, section of the skin of æsophagus .. 26

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