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The sense of hearing-Organs of sound-Mollusca-Crustacea—
Insects Locusts - Grasshoppers - Crickets - Cicadas -
Beetles-The bombardier beetle-Paussus-Death-watch-
Burying beetles-Weevils-Cockchafers-Variety of organs
of sound among beetles-Diptera-Hymenoptera—Ants—
Bees--Sounds produced in flight-Power of varying sound
-Butterflies-Moths-Centipedes-Spiders-Power of hear-

ing in insects-Sense of hearing in insects

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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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Eu-

of Crustacea-Structure of eye-Mysis-Corycæus-Copilia
-Calanella-Limulus-Scorpions-Light-organs of
phausia-Mode of vision by compound eyes-Müller's theory
of Mosaic vision-Images thrown by the cornea-Objections
to other theories-Position of the image-Absence of power
of accommodation-Absence of retina-Summary-On the
power of vision in insects-Experiments on vision of insects

.-On the function of ocelli-Difficulty of subject-Experi-

ments-Short sight of ocelli-Ocelli of cave-dwelling spiders

-Probable function of ocelli

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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

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LIST OF ILLUSTRATIONS.

FIGURE

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

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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

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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; 7, lens; o, optic nerve; g, 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

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10. Papilla from the surface of the hand, × 350. a, Cone-like body; b, nerve; c, end of nerve

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11. Portion of the skin of the back of the hand. The centre figure represents the arrangement of the hairs; CP, the cold-points;

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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; nr1, 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. lb, Tactile hair;

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LIST OF ILLUSTRATIONS.

FIGURE

PAGE

hy, hypoderm; c, cuticle; b, anterior part of brain; ɑ, eye;
ne, nerve-fibrils; v, anterior blood-vessel

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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 epithelial cells; c, cellular body; d, cells; n, nerve

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 capsule wall, and terminating in b', b', 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 termination of sense-organ; e, nerve given off by one sense-organ to another, b"

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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
19. Part of the proboscis of a fly (Musca). n, nerve; g, ganglionic
swellings; s, tactile hairs or rods; c, cuticle

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20. Right half of eighth segment of the body of the larva of a guat (Corethra plumicornis). EG, Ganglion; N, nerve; g, auditory ganglion; gb, auditory ligament; Ch, auditory rods; a, auditory nerve; e, attachment of auditory organ to the skin; b, attachment of auditory ligament; hn, hn', termination of skin-nerve; tb, plumose tactile hair; h, simple hair; ty, ganglion of tactile hair; Im, longitudinal muscle

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21. Taste-buds of the rabbit, × 450 ..

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22. a, Isolated taste-cells from the mouth of a rabbit; b, two covercells and a taste-cell in their natural position, × 600

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, × 600

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24. Inner layer of skin of the proboscis of Asterope candida, × 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', a b c d e f, section of the skin of œsophagus

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