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INTERNATIONAL SCIENTIFIC SERIES
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-

THE INTERNATIONAL SCIENTIFIC SERIES

ON THE SENSES
INSTINCTS, AND INTELLIGENCE
OF ANIMALS

WITH SPECIAL REFERENCE TO INSECTS

BY

Sir JOHN LUBBOCK, Bart.
i? PF BS. D: ¢: L.,.. LL.D.
AUTHOR OF ‘‘ ANTS, BEES, AND WASPS ;”’ ‘‘ PREHISTORIC TIMES,” ETC.

WITH OVER ONE HUNDRED ILLUSTRATIONS

NEW YORK
fiat PLETON AND COMPANY
: 1888

Transfer
Enginee rs School Liby,
‘June 29,1931

PERE FACE,

—

In the present volume I have collected together some
of my recent observations on the senses and intelli-
gence of animals, and especially of insects.

While attempting to understand the manners and
eustoms, habits and behaviour, of eee as well as for
the purpose of devising test experiments, I have found
it necessary to make myself acquainted as far as possible
with the mechanism of the senses, and the organs by
means of which sensations are transmitted. With this
object I had to look up a great number of memoirs, in
various languages, and scattered through many different
periodicals ; and it seemed to me that it might be inte-
resting, and save others some of the labour I had to
undergo myself, if I were to bring together the notes
I had made, and give a list of the principal memoirs
consulted. I have accordingly attempted to give, very
briefly, some idea of the organs of sense, commencing

in each case with those of man himself.

al PREFACE.

Mr. John Evans, Dr. M. Foster, and my brother, Dr.
Lubbock, have been so kind as to read through the
proofs, and I have to thank them for many valuable
suggestions. Lord Rayleigh also has been so good as
to look at the chapters on Hearing.

Hiego Etms, Down, Kent,

CONTENTS.

CHAPTER L
_ PAGE
Introductory remarks—Difficulty of the subject—The life of a
cell—Possible modes of origin of sense-organs—Origin of
eye and ear—The sense of touch—The organs of touch—
Nerves of touch—Sense of temperature—Cold points—Heat
points — Pressure-points—Organs of touch among lower
animals — Medusze — Annelides—Mollusca—Crustacea—In-
sects—Sense-hairs—Tactile hairs aes -- EEE 1

CHAPTER II.

The sense of taste—Taste-organs of man—Mammalia—Birds—
Reptiles—Taste-organs of the lower animals—Crustacea—
Insects—Sense of taste in insects—Organs of taste in

_ insects—The bee—Humble bee—Wasp—Fly—Individual
differences .., ni: see ve aa eho

CHAPTER III.

The sense of smell— Protozoa and Ceelenterata— Worms— Mollusca
—Insects—Seat of the sense of smell—Different theories as
to the seat of the sense of smell in Insects—Experiments
with Dinetus — Hydaticus — Silpha — Stag-beetle — Ants—
Seat of the sense of smell partly in the palpi, partly in
antenne—Organs of smell—Leydiyg’s olfactory cones—
Organs of smell in Crustacea—Centipedes—Olfactory
cones in insects—Olfactory hairs—Olfactory pits—Ol-
factory organs of fly—Antenna of Ichneumon—Olfactory
organs of wasp—Antennal organs of insects—Complex
structure of the antennze—Various uses of antcnnz aumeh Oa

Vill x CONTENTS.

CHAPTER IV.

PAGE
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—A nts—
Bees—-Sounds produced in flight—Power of varying sound
—Butterfliles—Moths—Centipedes—Spiders—Power of hear-

ing in insects—Sense of hearing in insects on » 60

CHAPTER V.

The organs of hearing—Structure of the human ear—The organ
of Corti—Mode of action of auditory organs—Organs of
hearing in the lower animals—Meduse—Auditory hairs—
Mollusca—Annelides—Crustacea—Use of grains of sand as
otolithes—Ear in tail of Mysis—Mode of hearing—Organs
of hearing in insects—Seat of the sense of hearing in insects
—Different seats of organs of sense—Kars in legs of crickets
—Ear of grasshoppers—Structure of ear—Auditory rods—
Kar of locusts—Peculiar structure in leg of ant—Origin of
ear—Ear of fly—Peculiar sense-organs—Auditory rods in
beetles—Position of auditory rods—Chordotonal organs—
Auditory hairs of antennez of gnat—Sympathetic vibrations
—Organs of hearing in various parts of body ane aoe,

CHAPTER VI.

The sense of sight—Three possible modes of sight—Different
forms of eye—The vertebrate eye—Structure of the eye—
The retina—The rods and cones—The blind spot in the eye
—Inversion of the rods—The pineal gland—The rudimentary
-Inedian eye—The median vertebrate eye—The organs of
vision in the lower animals—Color-spots—Echinoderms—
Worms—Molluses—Cuttle-fish—Compound eyes in Molluses
—Arca—Spondylus—Pecten—Onchidium—Sense-organs of
Chiton woe oe +f aes =a sas) See

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—LHyes

CONTENTS.

of Crustacea—Structure of eye—Mysis—Corycseus—Copilia
—Calanella—Limulus—Scorpions—Light-organs of Eu-
phausia—Mode of vision by compound eyes—Miiller’s theory
of Mosaic vision—Images thrown by the cornea—Objections
to other theoriés—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_ ... ve coe vee

CHAPTER VIII.

On problematical organs of sense—Muciferous canals of fish—

On

Deep-sea fish—Light-organs—Living lamps—Problematical
organs in lower animals—Meduse—Insects—Crustacea—
Difficulty of problem—Size of ultimate atoms—The range
of vision and of hearing—Unknown senses—The unknown
world oes oo = sae cee eee

CHAPTER IX.

bees and colors—Experiments with colored papers—Dr.
Miiller’s objections—Reply to objections—Preferences of
bees—The colors of flowers... bop oe wee

CHAPTER X.

the limits of vision of animals—Ants and colors—The
ultra-violet rays—The limits of vision in ants—Supposed
perception of light by the general surface of the skin—
Experiments with hoodwinked ants—Confirmation of my
experiments on ants—Experiments with Daphnias—Daph-
nias and colors—Preference for yellowish green—HExperi-
ments—Limits of vision of Daphnias—Perception of
ultra-violet rays—Objections of M. Merejkowski—Suggestion
that Daphnias perceive brightness, but not color—Further
experiments—Evidence that Daphnias perceive differences
of color pee ae sae _ one eae

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

1x

PAGE

146

182

194

202

x CONTEN'IS.

PAGE
pup and subsequently restored—Experiments with drowned
ants—Recognition after a year and nine months—Supposed
recognition by scent—Recognition by means of the antennz 232

CHAPTER XII.

— On the instincts of solitary wasps and bees—Instinct of render-
ing victims insensible—Origin of instincts—Habits not
invariable—Change of instincts—Bembex—Odynerus—Am-
mophila—Modifiability of instincts—Differences under
different circumstances—Origin of the habits of Sphex—
Race differences—Limitation of instinct—Toleration of para-
sites—Cases of apparent stupidity—M. Fabre’s experiments
—Limitation of instinct—Instinct and habits—Inflexibility
of instinct— Different habits of males and females—Arrange-
ment of male and female cells—Power of mother to regulate
the sex of the young ... se esp chs kA! ieee

CHAPTER XIII.

' On the supposed sense of direction—Experiments with bees—
Whirling bees—Behaviour of bees if taken from home—
Mode of finding their way—Experiments with ants—Mr.
Romanes’ experiments—No evidence of separate sense
of direction .. eee ieee vee eee ss ee

CHAPTER XIV.

On the intelligence of the dog—Education of the deaf and dumb
—Laura Bridgman—Application of the method followed
with the deaf and dumb to animals—My dog Van and his
cards—Use of cards with words on them, “ food,” “ water,”
“tea,” etc.—Recognition of the separate cards—Association
of the card with the object—Realization that bringing a
card was a request—Attempts to convey ideas—Arithmetical
powers of animals—Previous observations—Supposed powers
of counting—Mr. Huggins’s experiments—Conclusion ... 272

LIST OF ILLUSTRATIONS.

FIGURE

12

ASD oP

ie.)

10.

12.

14,

15.

Diagram to illustrate possible origin of asense-organ. ¢, a
h, cellular or hypodermic layer Ee ee

. Diagram to illustrate possible origin of a sense-organ. ¢, Cuticle

h, cellular or hypodermic layer

. Diagram to illustrate possible origin of a sense-organ. ¢, Onticke

h, hypoderm; n, nerve

. Diagram of further stage in the origin af a sense-organ

. Diagram illustrating a second possible origin of a sense-organ

. Diagram of further stage in the origin of a sense-organ e
. Section through the simple eye of a young Dytiscus larva. A,

Hypoderm ; /, lens; 0, optic nerve; g, p, modified hypodermic
cells; r, retina .. -: ce ye Ks ie ie

. Auditory vesicle of Ontochis oe oe cs
. Pacinian corpuscle. a, Neuriiemma; ne nerve- fibril’ c, capsule ;

d, peculiar fibres; e, central feslitaley a
Papilla from the surface of the hand, x 350. a, ees like wade :
b, nerve; c, end of nerve ‘ ae

. Portion of the skin of the back of ie hind. The pkee: figure

represents the arrangement of the hairs; CP, the cold-points ;
WP, the warmth-points ..

Half a cross section through the brain a Binder 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 ..

. Part of upper nerve-ring and tactile epithelium of Lizzia. a,

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

Glandular cell; »z, nervous cell : as a a
Anterior part of body of Bohemilla comata. 1b, Tactile hair;

PAGE

3

3

or ou

10

12

13

X11

LIST OF ILLUSTRATIONS.

FIGURE

hy, hypoderm ; ¢, cuticle; 6, anterior part of brain; a, eye;
ne, nerve-fibrils ; v, anterior blood-vessel a es ae

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

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; d, cells; n, nerve a =f

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

18

19.

20.

21.

22.

23.

24.

25.

in the tegmentum of ashell 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; A, iris;
g, lens; %, pigmented capsule of eye; n, optic nerve; 7, rods
of retina; n’, branches of the optic nerve, perforating the cap-
sule wall, and terminating in 0’, 0’, b’, ocular sense-organs ;
p, Pp, 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 ; ¢, nerve given off by one sense-organ
to another, 0” .. Be a oF : a ae

Diagram of forms of hairs in insects. a, Or avals surface hair;
6, plumose natatory hair; c, hair of touch; d, auditory hair;
e, olfactory hair; f, taste hair; n, nerve Hat me i

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

Right half of eighth segment of the body of the larva of a feat
(Corethra plumicornis). EG, Ganglion; N, nerve; g, auditory
ganglion; gb, auditory ligament; Ch, auditory rods; a, auditory
nerve; é, attachment of auditory organ to the skin; 0, attach-
ment of auditory ligament ; hn, hn’, termination of skin-nerve;
tb, plumose tactile hair; A, simple hair; tg, ganglion of tactile

hair; 7m, longitudinal muscle .. - a a --
Taste-buds of the rabbit, x 450 .. Le “x _
a, Isolated taste-cells from the mouth of a vibe. b, two cover-
cells and a taste-cell in their natural position, xX 600 _ ..

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 .. e*

Inner layer of skin of the aietaia of pie ope a Xx 400.
a, Cuticle; 6, terminal (merve) organs; c, ganglionic cells;
d, longitudinal muscle; e, transverse muscle .. i :

Taste-organ of the bee. B, Horny ridge; R, R, sensory jie
C, C, skin of the mouth; Z, muscular fibres; A, A, muscular
fibres; S, S', abcde f, section of the skin = esophagus ..

PAGE

13

14

15

16

17

18
20
20
21

22

26

LIST OF ILLUSTRATIONS.

FIGURE

26.

27.
28.
29.
30.
31.

32.

33.

34.
35.

36.

41.
42.

Shows three of Wolff’s cups, each with a central hair, a chitinous
ring, and a double ganglionic swelling terminating in a nerve-

‘fibre, x 500 times. R, R’, Sensory pits and hairs; G, G,
ganglionic swelling of nerve .. ee oe oe ee

Under side of left maxilla of Vespa. Gm, Taste-cups ; Shm, pro-
tecting hairs; Jb, tactile hairs; M¢, base of maxillary palpus

Section through a taste-cup. SK, Supporting cone; JN, nerve;
SZ, sense-cell <2 aa

Tip of the proboscis in the hive et (Apis), 4 140. LI, Terminal
ladle; Gs, taste-hairs; Sh, guard-hairs; Hb, hooked hairs ..

Organ of taste of fly (Musca vomitoria). gn, Nerve; gg, ganglion ;
ax, axe-cylinder; gc, terminal cylinder; gf, terminal cone

Epithelial and (B) olfactory cells of man.

Cells from the olfactory region of a iiotdas (after Stricker). ay
Epithelial cells; 6, the apparent processes; ¢, olfactory cells.
_ elie.

Section through the fiead seaman of Balyephthalivas, “ 300.
lmd, muscle; 6o, cup-shaped organ; cu, cuticle; hp, hypo-
derm ; /md, longitudinal dorsal muscle; m, peripheral nerve;
b, cerebral ganglion; cz, commissure of brain; mb, membrane;
pmg, pigment cells; Apdz, unicellular eet in the ee
gn, brain; &, clad in the brain -

Antenna of Panteilis Bairdii (Lubbock) .

Terminal segments of one of the smaller satan of the ator
woodlouse (Asellus aquaticus), X 500. a, Ordinary hairs (not
connected with a nerve); 6, hairs of eich (with a nerve at
the base); c, special cylinders (olfactory cylinders) .

Tip of the antenna of a centipede (Julus terrestris), X 600. At
the apex are four olfactory cylinders, a few of which are also
seen on the following segment, among the ordinary hairs

. End of a palpus of Staphylinus erythropterus, X 600. a, Olfac-

tory pit .. o> e°

. Part of antenna of Giiiatsen ane ranea. 0, Otfactory hairs

g, peculiar curved hairs .

. Terminations of olfactory ne of hishatcs. a, Of ‘aes af 3 a

Paleemon; }, of a Pagurus; ¢, of a Pinnotheres; d, of a Squilla;
e, of a Pontonia ..

. Antenna of blowfly. a, Enlarged third segment, showing pits ;

c, base of the antenna
One segment of the antenna of an ae =
Section through part of the antenna of a wasp, X 430. CH,

. Chitinous skin; Z, olfactory cone; G, olfactory pit; TB, tac-

xill

PAGE

27

28

28

29

30

33

33

34
47

48

49

50

50

51

53
o4

XIV. LIST OF ILLUSTRATIONS.

FIGURE PAGE
tile hairs; H, hypodermic cells; M, the membrane surrounding
them; 4, nuclei of the olfactory cell; X,, remains of the
~ earlier upper nucleus; SX, lower circle of rods; RS, olfactory.
rod; GZ, Geisselzelle; M/Z, membrane forming cell; 1, mem-
brane closing the pit .. ‘ ay. as oe
43. Diagram showing structures on the fers soginaet of the
antennz of insects. a, Chitinous cuticle; 6, hypodermic layer ;
6, ordinary hair; d, tactile hair; e, cone; f, depressed hair,
lying over g, cup, with rudimentary hair at the base; h, simple
cup; 7, champagne-cork-like organ of Forel; &, flask-like

organ; /, papilla, with a rudimentary hair at the apex =<. pao
44, Leg of Stenobothrus pratorum .. as <- oe --. (2
45. Sound-bow of Stenobothrus “ 63

46, Diagram of humanear. D, Auditory ual K, pet of Eusta-
chian tube; cc, tympanic membrane; B, a cavity 5 0,
fenestra ovalis; r, fenestra rotunda; s, semicircular canals;

A, cochlea = ee ~ a6 “2 Me ce es

47. Ossicles of the ear. H, Hammer; Am, anvil; Am. 2, shorter

process of the anvil; Am. 7, longer process of the anvil; S,

stirrup; Sz, long process cf the hammer =: -- a) eo
48. Section through the ampulla. WJ, nerve; z, terminal cells; A,
auditory hairs .. os oe : ° ne ae

49, eles wall of the ductus cochlearis, or Bie dog. ‘Gortice
- view from the side of the scala vestibuli, after the removal of
Reissner’s membrane, 39 [. Zona denticulata Corti. II. Zona
pectinata Todd-Bowman: i, Habenula sulcata Corti; 2, Ha-
benula denticulata Corti; 3, Habenula perforata Kolliker.
III. Organ of Corti: a, portion of the lamina spiralis ossea
(the epithelium is wanting); 6 and ¢, periosteal blood-vessels ;
d, line of attachment of Reissner’s membrane; é and @,, epi-
thelium of the crista spiralis; f, auditory teeth, with the
interdental furrows; g, g,, large-celled (swollen) epithelium
of the sulcus spiralis internus, over a certain extent shining
through the auditory teeth; from the left side of the pre-
paration they have been removed; h, smaller epithelial cells
near the inner slope of the organ of Corti; 4, openings through
which the nerves pass; 7, inner hair cells; /, inner pillars;
m, their heads; 0, outer pillars; n, their heads; p, lamina
recticularis; g, a few mutilated outer hair cells; r, outer
epithelium of the ductus cochlearis (Claudius’s cells of the
author’s) ; removed at s in order to show the points of attach- _
ment of the outer hair cells... rs o* ee _. 8

LIST OF ILLUSTRATIONS.

FIGURE
50. ELutima gigas ae es ve ; ae ve be
51. Auditory organ of Ontorchis Daadtiands ws

.52. Auditory organ of Phialidium. d', Epithelium of ete upper
surface of the velum; d?, epithelium of the under surface of
the velum ; AA, auditory hairs; A, auditory cells; np, nervous
cushion ; m7’, nerve-ring ; 7, circular canal at the edge of the
velum ..

53. Auditory organ of cibeagatonsiwat still eA el a saath criti
kk, Modified tentacle; 0, auditory organ _

54, Sense-organ of Pelagia. o, Group of crystals, sk, sense- ain
sf, fold of the skin; ga, gastro-vascular channel .. “e

55. Auditory organ of Unio. a, Nerve; 0, cells; ¢, ciliz; d, otolithe
56. Auditory organ of Pterotrachea Friderici. Na, Auditory nerve;
c, central cells; d, supporting plate; 6, outer circle of audi-
tory cells; a, ciliated cells .. : is nie :
57. Base of right antennule of lobster Gavin marinus). a, Orifice 3
S, Sac :
58. Interior of idiom sac of ighetes a, fica: a canine waits
59. Part of wall of auditory sac of lobster (Astacus marinus). a,
Thickened bars in the membrane of the sac; y, first row of
auditory hairs; 7’, second row of auditory hairs; 7”, third row
of auditory hairs ; 7”, fourth row of auditory hairs ; e, grains
of sand, serving as otolithes : are o~ <¢
60. Auditory hair of crab (Carcinus diag 000. a, Skin; «,
nerve; , delicate intermediary membrane or hinge.. oe
61. Mysis ae =. oe os
62. Tail of Mysis tia showing the mudiiory organ -
63. Part of the leg of a grasshopper (Gryllus). 0, ¢, n, 6, ty ae te
64. Section through the tibia (leg) of a Meconema, x about 150.
tr, tr, The two trachee ; ar, the auditory rod ; ;
65. The tracheze and nerve- bani organs from the tibia (leg) of a
grasshopper (Ziphippigera vitium). EBT, Terminal vesicles of
Siebold’s organ; HT, hinder tympanum; Sp, space between
the trachea; Zr, hinder branch of the trachea ; SV, nerves
of the organ of Siebold; go, supra-tympanal ganglion; Gr,
group of vesicles of the organ of Siebold; vN, connecting
nerve-fibrils between the ganglionic cells and the terminal
vesicles ; So, nerve terminations of the organ of Siebold ; ol,
front tympanum; v7, front branch of the trachea . ae
66. Auditory rod of a grasshopper (Gryllus virions). oe
Auditory rod ; 4o, terminal piece
67. Diagram of a eet through the auditory organ ae a eee

XV

PAGE
83
84

85

85

86

87

87

88
88

89
92
92
93
98

102

103

104

XV1 LIST OF ILLUSTRATIONS.

FIGURE
hopper (Meconema). oe, Cuticle; a.r, ae rou 3 “a6;
auditory cell; tr, trachea - 2

68. Outer part of a section through the tibia of 3 a Crain viri-

PAGE

105

dissimus. h, Hard surface of leg; tr, trachea; F, fat bodies; —

Su, suspensor of the trachea; v W, tracheal all ; DN, nerve;
gz, ganglionic cells; rb, tissue connecting the ganglionic cells;
E. Sch., end tubes of the ganglionic cells, each containing an
auditory rod; fa, terminal threads of ditto .. of ae
69. Tibia of yellow ant (Lasius flavus), x 75. 8S, S, Swellings of
large trachea; rt, small branch of trachea; a, auditory organ
70. Part of the tibia of Zsopteryx apicalis. Sc, Auditory organ;
ef, terminal filament; Cu, cuticle; G, ganglionic cell; Se,
structure enclosing the auditory rod; tr, trachea; n, nerve
71. One of the halteres of a fly =
72. Right half of eighth segment of the God of the 1 va of a aie
(Corethra plumicornis). EG, Ganglia; N, nerve; g, auditory
ganglion; gb, auditory ligament; Ch, auditory rods; a, audi-
tory nerve; é, attachment of auditory ligament to the skin;
hn, hn', termination of skin-nerve; 7), plumose tactile hair;
h, simple hair; fg, ganglion of tactile hair; /m, longitudinal

muscle .. a os = se oe a ae
73. Head ofa gnat .. A's ae =. ae
74. Diagram showing one possible widde of ¥ Vision .. oe oe
75. Diagram showing a second possible mode of vision .. heh
76. Diagram showing a third possible mode of vision ee

77. Diagram of human eye. G, Vitreous humor; JZ, lens; W,
aqueous humor; ¢, ciliary process; d, optic nerve; ¢ é, sus-
pensory ligament; & &, hyaloid membrane; f f, h A, cornea;
g, choroid ; 7, retina; /, ciliary muscle; m/f, nf, sclerotic coat ;
p Pp, iris; s, the yellow spot. = — o- =

78. Section through the retina. 1, Limitary membrane; 2, layer
of nerve-fibres ; 3, layer of nerve-cells; 4, nuclear iayer; 5,
inner nuclear layer; 6, intermediate nuclear layer; 7, outer
nuclear Jayer; 8, posterior ae ara: 9, layer of small rods
and cones; 10, choroid . ; :

79. A, Inner Memetis of rods a S, Ss) and cones oe By Pode man,
the latter in connection with the cone-granules and fibres as
far as the external molecular layer, 6. In the interior of
the inner segment of both rod and cone fibrillar structure is
visible. x 800 - =. oe

80. Diagram to fe the existence of the blind ane in the eye

81. Pineal eye-scale on the head of a small lizard (Calotis) ee

106

107

109
110

114
115
119
119
120

121

123

124
125
127

LIST OF ILLUSTRATIONS.

FIGURE

82.

83.
84.

85.
86.
87.

88.

89.

21.
92.

93.
94.
95.

96.

97.

Diagram of a section through the skull and pineal eye of Lacerta
viridis. C, Cuticle; Pa, parietal bone; Ep, epidermis; J,
lens; Pig, Pigment; FR, rete mucosum; CH, cerebral hemi-
sphere; NV, nerve; Lp, epiphysis ; es optic lobe of brain

Englena viridis. e, Eye-spot .. -F

Section through the simple eye of a young By ieee bers: l,
Corneal lens; g, cells forming the vitreous humor; 7, retina;

0, optic nerve; A, hypoderm .. ae o- -¢
Eye-spot of Lizzia. oc, Ocellus; /, lens E ate ais
Eye-bulb of Astropecten .. d ae oe
Eye of Asteracanthion. , Cuticle; é, pai ica: /, lens; p,

pigment . 28 os os .

Anterior eeaeaity of a ‘Sedierites worm (Bohemilla eras
a, Kye; 6, brain; ¢, cuticle; Ap, ee lb, tactile hair ;
mé, nerve; 2, easel 2 : me oe

Eye-dot of Nereis. In B the pigment is eis fumoned sO as
to show the lens oe

. The first twelve segments of Batcgsieleajes pe ee seen from

below. The Roman numerals indicate the segments. St,
Papillz on the head; KS, head ; au, head eye; s.au, side eyes;
Ol, upper lip; U7, under lip; v.ph, pharyngeal vein; V.subinta,
anterior ventral vein; V.d.J!-+, veins connecting the superior
lateral and vessels; sept'—*, intersegmentary membranes;
m.ocs.l, lateral muscle of the esophagus; V.ann, pulsating
circular vessel; Md.dr, stomach-glands; V.v-/, vein con-
necting the inferior and lateral blood-vessels; Md, stomach ;
Bm, muscles of the hairs; G, brain; fi.o, ciliated organ; gm,

transverse muscle =a a -# ae Sc ae
Alciope
Perpendicular fection phcasck ihe are of a dane (Patella).
1, Epithelial cells; 2, retina cells; 3, vitreous body --
Eye of Trochus magus. Gl, Vitreous body; No, nerve ar

Eye of Murex brandaris. L, Lens; Gl, vitreous body; No, nerve
Eye of Helix pomatia. ct, Cuticle; a, epithelium; 6, cornea;
c, envelope of the eye; d, cellular layer; e, fibrils of the optic
nerve; jf, feeler cell; na, nerve of the 5 as no, optic
Herve... & az)
Perpendicular seetion thr ae an eye of head noe. 1, Epithe-
lium of the edge of the mantle; 2, cells of vision; 3, lens;
4, 5, connective tissue; 6, section of one of the cells ae
Diagram of eye of Pecten. a, Cornea; 0, transparent basement
membrane supporting the epithelial cells of cornea; c, the

136
137

138
138
139

140

142

XVill LIST OF ILLUSTRATIONS.

FIGURE

98.

a2.

100.
101.

102.

103.

104.

105.
106.

107.
108.

pigmented epithelium; d, the lining epithelium of the mantle;
e, the lens; f, the ligament supporting the lens; g, the
retina; fh, the tapetum; &, the pigment; m, the retinal
nerve; ”, complementary nerve oe a

Schematic representation of the soft and some of the hand par fs
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 ; 0, 6’, ends of nerve; c, nerve; f,
calcareous cornea; g, lens; /, iris; %, pigmented capsule of
eye; m, body of sense-organ cut across; ”, nerve of eye; p,
nerve of sense-organ ; 7, rods of retina :

Long section through the front (A) and hinder (B) oa ones
of Epeira diadema. A, Anterior eye; 3, posterior eye; Hp,
hypoderm; Cé, cuticle ; ct, boundary membrane; JZ, muscular
fibres; I, UM’, cross sections of ditto; St, rods; Pg, P', pig-
ment cells; Z, lens; Gé', vitreous body ; K, nuclei of the cells
of the retina; K¢, crystalline cones; At, retina; Nop, optic nerve

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

Section throngh the eye of a fly. 6.m, Basilar membrane; ec,
cuticle; e.op, epioptic ganglion; .c, nuclei; x.c.s., nerve-cell
sheath; NV.f, decussating nerve-fibres; op, optic ganglion; pe,
pseudocone; pg, pigment cells; p.op, perioptic ganglion; r, re-
tinula; AA, rhabdom; 7, trachea; ¢.a, terminal anastomosis;
Tt, Hieh ans ti, tracheal vesicle x i

Two separate Aches of the faceted eye of a *s Lf, Cornea ;
n, nucleus of Semper; 2, crystalline cone ; Pg, a ae
cells; Al, retinula; Rm, rhabdom —..

Eyelet of cockroach. Jf, Cornea; &f, Gevtalinas cone; pq’, pig-
ment cell; r/, retinula; rm, rhabdom ee

Eyelet of cockchafer. (f,Cornea; &&, crystalline cone ; a oh :
pigment cells; rl, retinula; rm, rhabdom .. a

Leptodora hyalina

Eye of Mysis. n, Nuclei; Lf, ve : E eryabaiains cones ;
n', cells of the retinula; &/, retinula; Rm, rhabdom; Cp,
bloog-vessels; , fibres of the optic nerve; N™, N13, N ee
decussations of the fibres of the optic nerve; G, G1, ganglia ;
M, muscles for the movement of the eye-stalk ; Km, nuclei ..

Coryceus. a, b, The eye : — ° . =e

Eyes of Calanella Mediterranea. Pg, pigment cells; N-fr,
frontal nerves; V.op, nervus opticus. The numbers show
the numbers of the cells

PAGE

143

145

147
148

149

150

152

a eee

156

157
158

159

LIST OF ILLUSTRATIONS.

FIGURE
109. Diagram of a vertical section through a portion of the lateral

eye of Limulus polyphemus, showing some of the conical lenses,
and corresponding retinule. a, Cuticle; 0, cuticular lens;

cc, hypoderm; £n, retinula; n, nerves ae Ait as
110. Euphausia pellucida. 1.0, Luminous organ... ie
111. Luminous organ of Zuphausia. f, Fibres; e, lens .. as

112. Eye-stalk of Huphausia. fo, Luminous organ; a, lower eye ..

113. One of the elements of the eye of a fly. 4k, Crystalline cone;
xz, position of the image; s, rod; sc, sheath; scm, outer
sheath; r, retina; y, seat of vision .. es :

114. Photichthys argenteus .. <= a a. ee ae

115. Ceratius bispinosus : : :

116. Edge of a portion of the santa of ain Monette with a
pair of sense-organs. v, Velum; 4, sense-organ; ro, layer of

nettle cells; ¢, tentacle ‘ :

117. Sense-organ of leech, 1, Epithelium 5 2, pigment 3, cee: :
4, nerve.. a

118. Daphnia pulex. a, Antecins 4 Te ains @, ee h, ee Mm,
muscle of eye; 7, nerve of eye; 0, ovary; ol, olfactory organ;
s, stomach; y, three eggs deposited in the space between the
back and the shell =: -- ec aa oe 5

X1xX

PAGE

189

211

LIST OF THE PRINCIPAL MEMOIRS, ETC.,
REFERRED TO IN THE PRESENT WORK.

Ahlborn, Zur Anat. und d. Ent. der Epi. b. Amphibien und Reptilien, Zool.
Anz., 1886.
Allman, Mon. of the Hydroids, Ray Society, 1871.

Becher, Zur Kenntniss der Mundtheile der Dipteren, Denkschr. der Acad.
d. Wiss. Wien., 1882.

Béla Haller, Untersuchungen itiber marine Rhipidoglossen, Morphol.
Jahrb., 1884.

Beraneck, Ueber d. Parietal Auge der Reptilien, Jenaische Zeitschrift,
1887.

Berger, E., Unt. i. d. Bau d. Gehirns u. d. Retina d. Arthropoden, Zool.
Inst. Wien., 1878.

Bernstein, The Five Senses of Man.

Bevan, On the Honey Bee.

Blainville, De, Principes d’anatomie comparée.

Blix, Exper. Beit. z. Lésung d. Frage wi. d. Specif. Energie d. Hautnerven,
Zeit. fiir Biologie, 1884.

, Exper. Beit. z. Lésung d. Frage ti. d. Specif. Energie d, Hautnerven,

Zeit. fiir Biologie, 1885.

Boll, F., Beitrage z. Phys. Optik, Arch. fir Anat. Phys. u. Wiss. Medicin,
1871.

Bonnsdorf, Fabrica, usus, et differentie palparum in insectis. Dissertatio.
Aboae, 1792.

Bourne, G. C., On the Anatomy of Spherotherium. Linnean Journal,
1885.

Boyes, Capt., The Economy of the Pausside, Ann. and Magazine of Natural
History, vol. xviii.

Brady, On the Copepoda of the Challenger Expedition, vol. viii.

2

Xxil MEMOIRS, ETC., REFERRED TO.

Breitenbach, Beit. z. Kennt. d. Baues d. Schmetterling-Riissels, Jenaische
Zeit., bd. xv.

Briant, T. T., On the Anatomy and Functions of the Tongue of the Bee,
Journal of the Linnean Society, 1864.

Buchner, L., Mind in Animals. ;

Burmeister, Handbuch der Entomologie. 1885.

Carriére, J., Die Sehorgane der Thiere. 1885.

Claparéde, E., Morphologie des zusammengesetzten Auges bei den Arthro-

poden. Zeit. fiir Wiss. Zool., 1860.

, Anat. and Ent. d. Retina, Miiller’s Archiv, 1857.

—, Sur les pretendus organes auditifs des Antennes chez les Colé-
optéres, Ann. Sci. Nat., 1858.

Claus, Ueber den Acoust. App. im Gehérorgane der Heteropoden, Arch.
fiir Mic. Anat., 1878.

, Ueber einige Schizopoden und niedere Malacostraceen, Zeit. fiir Wiss-
Zool., 1863.

Comparetti, Dinamica animale degli insetti. Padoue: 1800.

, De aure interna comparata-Patavii. 1789.

Cornalia, Monografia del Bombice del Gelso, Mem. d. R. istit. Lombardo di
science. Milano: 1856.

Dahl, Das Gehér-und Geruchsorgan der Spinnen, Arch. fur Mik. Anat.,
1885.

Darwin, Descent of Man.

, Earthworms.

, Origin of Species.

Desvoidy, Robineau, Recherches sur l’organisation vertébrale des crustacés
et des insectes.

Donhof, Bienenzeitung, 1851 and 1854.

Dor, De la Vision chez les Arthropodes, Arch. d. Sci. Phys. et Nat. Genéve:
1861.

Duméril, Considérations générales sur les insectes.

Du siége de la gustation chez les coléoptéres, Comptes rendus del’ Acad. d.
Sciences, 1886.

Eimer, Dr. Th., Ueber Tast-apparate bei Eucharis multicornis, Arch.
fur Mic. Anat., 1880.

Erichson, De fabrica et usu antennarum in insectis. Berlin: 1847.

Exner, 8., Ueber das Sehen von Bewegungen und die Theorie des zusam-
mengesetzten Auges. Sitzungsber, Wien. Akad., 1875.

——, Die Frage der Functionsweise der Facettenaugen, Biol. Centraiblatt,
1881, 1882.

MEMOIRS, ETC., REFERRED TO. * REE

Fabre, J. H., Souvenirs Entomologiques. Etudes et Instinct sur les Meurs
des Insectes, 1879.

, Nouveaux Souvenirs Entomologiques. 1882.

, souvenir Entomologiques, troisiéme série. 1886.

Farre, On the Organ of Hearing in Crustacea, Phil. Trans., 1843.

Forel, A., Les fourmis de la Suisse, Genéve.

, Expériences et Remarques Critiques sur les Sensations des Insectes,

Recueil Zool. Suisse, 1887.

Fraisse, Ueber Molluskenaugen, Zeit. fiir Wiss. Zool., 1881.

Gazagnaire, J., Orig. de la gust. chez les coléoptéres, Proc. verb. de la Soc.
Zool. de France, 1886.

Gegenbaur, Beit. zur Kennt. der Gastropodenaugen, Gegenbaur’s Morph.
Jahrbuch, 1885.

, Elements of Comparative Anatomy.

Gersticker, Beschreibung neuer Arten der Gattung Apion, Ent. Zeit.,
Stettin, 1854.

Goldschneider, Dr. A., Monath. fiir prackt. Dermatologie, 1884.

, Die spezif. Energie der Temperaturnerven.

——, Die spezif. Energie der Gefiihlsnerven der Haut. ibid.

, Neue Thatsachen iiber die Hautsinnesnerven, Zool. Anz., 1885, 1886,

Gottsche, C. M., Beitrag zur Anatomie und Physiol. des Auges der Fliegen
und Krebse, Muller’s Arch. fur Anat. und Phys., 1852.

Graaf, De, Zur Anat. und Ent. der Epi. b. Amphibien und Reptilien, Zoo/.
Anz., 1886.

Graber, Dr. V., Die Gehérorgane der Heuschrecken, Arch. fur Mic. Anat.,
1875.

——, Die Tympanalen Sinnesapparate der Orthopteren, Denkschr. d. Kais.

. Akad. Wiss. Wien., 1876.

———, Ueber neue otocystenartige Sinnesorgane der Insekten, Arch. fiir Mic.
Anat., 1879.

———, Ueber das unicorneale Tracheaten-und speciell das Arachnoiden-und
Myriapoden Auge, Arch. fiir Mic. Anat., 1879.

——, Die Chordotonalen Sinnesorgane und das Gehér der Insekten, Arch.
fur Mic. Anat., 1882.

——, Morphologische Untersuchungen iiber die Augen der freilebenden
Marinen Borstenwiirmer, Arch. fur Mik., 1880. :

——, Fundamental Versuche iiber die Helligskeits und Farben Empfind-

lichkeit augenloser und geblendeter Thiere, Sitz. Kais Acad. d. Wiss.

Wien: 1883.

, Vergleichende Grundversuche iiber die Wirkung und die Aufnan-

mestellen chemischer Reize bei den Thieren, Biol. Centralblatt, 1885.

XXIV MEMOIRS, ETC., REFERRED TO.

Graber, Dr. V., Ueber die Helligkeits-und Farbenempfindlichkeit einiger
Meerthiere, Sitzungs-Ber., Akad. Wien., 1885.

Greeff, R., Untersuchungen iiber die Alciopiden Nova acta Acad. Leopold.
Carel 1876.

——, Untersuchungen iiber die Alciopiden. Nova acta Acad. Leopold.
Can. 1878.

Grenacher, H., Zur Entwicklungsgeschichte der Cephalopoden, Zeit. fur
Wiss. Zool., 1874.

-——, Abhandlungen zur vergleichenden Anatomie des Auges. Das Auge
der Heteropoden. Abh. Halle: 1886.

——, Untersuchungen iiber das Sehorgan der Arthropoden. Gottingen:

1879.

, Ueber die Augen einiger Myriapoden, Arch. fur Mic. Anat., 1880.

Grobben, Ueber blischenférmige Sinnesorgane u. eigenthiimliche Herz-
bildung der Larva von Ptychoptera contaminata, Sitz. der K. Akad. der
Wiss. Wien: 1876.

Grube, E., Ueber Augen bei Muscheln., Muller’s Arch. fiir Anat. und
Phys., 1840.

Giinther, Challenger Reports, vol. xxvii.

, Introduction to the Study of Fishes.

Haeckel, K., Ueber die Augen und Nerven der Seesterne, Zeit. fur Wiss.
Zool., 1860. |

Haller, G., Z. Kenntn. der Sinnesborsten der Hydrachniden, Wiegmann’s
Arch. ‘fiir Naturgesch., 1882.

Hauser, Physiologische und histol. Untersuchungen tiber d. Geruchsorgan
der Insecten, Zeitschrift fur Wiss. Zoologie, 1880; et Bullet. de la Soe.
des amis des Sci. Nat. de Rouen, 1881.

Helmholtz, Sensations of Tone.

Hensen, V., Ueber das Auge einiger Cephalopoden, Zeit. fiir. Wiss. Zool.,

1865.

, Ueber das Auge einiger Lamellibranchiaten, Zeit. fur Wiss. Zool., 1865.

——, Ueber das Gehororgan von Locusta, Zeit fur Wiss. Zool., 1866.

, Ueber den Bau des Schneckenauges, Arch. fiir Mik. Anat., 1866.

Hertwig, O. und h., Das Nervensystem und die Sinnesorgane der Medusen.
Leipzig: 1878.

——,R., Das Auge der Planarien., Sitz. der Jenaischen Gesch. fiir Med.
Naturwiss, 1880.

Hicks, On a New Structure in the Antennae of Insects, Jour. Linn. Zool., 1857.

, Further remarks on the organ found in the bases of the halteres and

wings of Insects, Zrans. Linn. Soc. Jour., 1857.

+——, On certain Sensorial Organs in Insects hitherto undescribed, Ann, of
Nat. Hist., 3rd ser., 1859.

MEMOIRS, ETC., REFERRED TO. XXV

Hickson, S. J., The Eye of Pecten, Quar. Jour. Mic. Soc., 1880.

——, The Eye of Spondylus, ibid., 1882.

, The Eye and Optic Tract of Insects, ibid., 1889.

Hoffmeister, Familie der Regenwiirmer. 18405.

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deutsch. Akad. d. Naturf., 1875.

ON THE
SENSES, INSTINCTS, AND INTELLIGENCE

OF

poy fk WE A 18.

CHAPTER I.
INTRODUCTORY REMARKS.

THE organs of sense may be said to be the windows
through which we look out into the world, and it has
always been to my mind one of the most interesting
. problems of natural history, to consider in what manner
external objects affect other animals, how far their
_ perceptions resemble ours, whether they have sensations
which we do not possess, and how we ourselves arrive
at our own perceptions.

I. propose to dwell in the present work especially on
the senses of insects, partly because my own observa-
tions have been made principally on them, and partly
because their senses have, perhaps, been on the whole
more thoroughly and successfully studied than those
of the other lower animals; which again arises from
the fact that no group offers more favourable oppor-
tunities for the study of these organs. The subject is
no less vast than difficult, and I do not pretend in any
way to give a complete view of the whole question,

~

Z DIFFICULTY OF THE SUBJECT.

but have selected those cases which seemed to me the
most suggestive, interesting, and instructive.

No one can doubt that the sensations of other animals
differ in many ways from ours. Their organs are some-
times constructed on different principles, and situated
in very unexpected places. There are animals which
have eyes on their backs, ears in their legs, and sing
through their sides. Nevertheless, in considering the
different senses, it will probably be most convenient to
begin by a short summary of our own organs, as afford-
ing the best clue to the purposes and functions of cor-
responding structures among the lower animals. The
subject is one of very great difficulty. Hven as regards
our own senses, we are still in extreme ignorance. The
clue afforded by anatomy is very imperfect, and some-
times almost misleading. No one can read the literature
relating to the organs of sense without feeling how
very little we really know on the subject. Even when,
as especially in the cases of the organs of hearing and
sight, we have careful and elaborate descriptions and
figures of very complex structures, these relate rather
to the separation and arrangement of the waves of sound
or light, than to the actual manner in which they affect
the nervous system itself; while as to the manner In
which our perceptions are in turn created, we are almost
absolutely ignorant. In the senses of taste and smell
this becomes, perhaps, even more clearly evident.

Every cell, indeed, in the animal body is a standing
miracle. Consider what it hastodo. It must grow; it
must assimilate nourishment; it must secrete; it must
produce other cells like itself; and this often in addition
to its own proper and distinctive function. The lowest
animals consist but of a single cell. Yet they feed and

THE LIFE OF A CELL. a

digest; they grow and multiply; they move and feel.
Their perceptions, indeed, are no doubt confused and
undifferentiated, and perhaps devoid of consciousness.
The soft protoplasm of which they consist is dimly
affected by external stimuli, as, for instance, by the
waves of light orof sound. These forms, however, are all
minute, and, indeed, almost invisible to the naked eye.
The larger animals are built up of a number of cells.

Let us, then, consider the possible modes in which an
organ of sense, say an eye, may have originated.

In the simpler forms, the whole surface is more or less
sensitive. Suppose, however, some solid and opaque
particles of pigment deposited in certain cells of the skin

Fig. 1.—Diagram of skin. c, Cuticle; A, cellular or hypodermic layer.

(Fig. 1). Their opacity would arrest and absorb the
light, thus increasing its effect, while their solidity would
enhance the effect of the external stimulus. <A further

Fig. 2.—Diagram of skin. ¢, Guiicle ob. cellular or hypodermic layer.

step might be a depression in the skin at this point,
which would serve somewhat to protect these differen-
tiated and more sensitive cells, while the deeper this
depression the greater would be the protection.

_ The epithelial cells frequently secrete more or less
matter, which may form a more or less solid ball.
This might be set in vibration by the sound-waves,
and would thus increase the effect on the epithelial

4. POSSIBLE MODES OF ORIGIN.

cells. Such a body is known as an otolithe. On the
other hand, it might serve as a lens, and by condensing

Fig. 3.—Diagram of origin of a sense-organ. c, Cuticle; h, hypoderm ;* n, nerve.

the light would act like a burning-glass, and increase
its effect on the cells below. A further stage would be

CC —_——__-
2d en a

Fig. 4.— Diagram of further stage in the origin of a sense-organ,
that the immediately subjacent cells, acted on by the
increased stimulus, might (Figs. 8 and 4) develop into

special nerve-tissue.
* Tie. the cellular layer below the cuticle.

OF SENSE-ORGANS. 5

‘Nor is thisa merely imaginary case. Hach of the above
stages may be found in actual existence—that, for in-
stance, indicated in Fig. 2 in the limpet (Fig. 92); Fig. 3,
in Trochus (Fig. 93); and Fig. 4 in the snail, Helix
or Murex (Figs. 94,95). Recent researches indicate
that the eyes of Articulata (insects, etc.) have, in some
cases at least, a similar history. But more than this,
if the development of the eye of an individual snail be
watched in the egg, it will be found to pass successively
through stages resembling Fig. 2, then Fig. 3, and
then Fig. 4.

In other cases, however, the organs of sense have a
different origin and history. Suppose, for instance,

Fig. 5.—Diagram of origin of a sense-organ.

that the hypodermic layer were at any spot (Fig. 9)
somewhat more strongly developed than elsewhere ; in
that ease, the cuticle secreted by the hypodermic aaie
would tend to be rather thicker than usual. This would
again (Fig. 6) constitute a lens, and serve to condense
the light. That certain eyes have actually arisen in
this way is indicated by Fig. 7, representing a section

Fig. 6.—Diagram of further stage in the origin of a sense-organ.

through the eye of the larva of a_ water-beetle
(Dytiscus). Nor, as we shall presently see, do these
two types of development by any means exhaust the
ways in which eyes may originate. In the two cases
given the eyes originate from the skin, but in others—
for instance, in ourselyes—the percipient elements are
formed irom the central nervous system.

6 ORIGIN OF EYE AND. EAR.

The tissues of the lowest animals have not been shown
to contain any special nerve-fibres, but underneath those
parts of the surface
where, either in the
mannerindicated above,
or in some other, the
effects of external stim-
uli are heightened by
any structural modifi-
cations, there would be
! a tendency to the speci-
Mig ang Dytiscus larve (after Grenachon), &, alization of an excep-

typoscrins felons: git nee: %. 2, tionally sensitive tissue.
Moreover, such an
organ as that represented in Fig. 4 might serve either
as a rudimentary ear or an eye. It might, indeed, be
acted on by the waves both of light and of sound. Such
organs—as, for instance, in the case of marginal bodies
round the edge of certain jelly-fishes (Meduse; see
Figs. 8 and 50)—have been regarded by some naturalists
as eyes, and by others as
ears. Haeckel suggests * that
some may be warmth-organs.

Fig. 8 represents one of the
marginal sense-organs of a
Medusa (Ontochis), where we
have a row of brilliantly re-
Deo ete desea” fractive spherules, whichsargm

analogy are considered to serve
as otoliths; but which, under other circumstances,
might be, and in fact have been by some, regarded
as the lenses of a simply constructed organ of vision.

* « Report on Deep Sea Meduse,” ‘‘ Challenger Reports,” vol. iv.

THE SENSE OF TOUCH. 7

Even among the most highly specialized organs of
sense, it is impossible not to be struck by the similarity
between the cones in the retina (Fig. 79) and certain
organs in the antennz of insects (Fig. 42) which are
generally considered as olfactory. It does not follow
that an organ with a nerve, a lenticular body, and
pigment, should necessarily be an eye. Nor, on
the other hand, is there anything in the structure
of the organs, for instance, of smell or taste which
throws any light on the perceptions we receive from
them. ‘That there should be separate nerve-fibrils in
our own skin, not only for the sensations of temperature
and of touch, but, as appears from the researches of
Blix and Goldschneider, even of heat and of cold, we
had not anticipated @ priori; and it would be difficult
to prove in any animal but ourselves.

THE SENSE OF ToucH.

I commence with the sense of touch, as being the
one which is most generally distributed, and from
which the others appear to have been in some cases
developed. The senses are not, indeed, as already
mentioned, always to be easily distinguished from one
another; and it would seem that the same nerve may
be capable of carrying different sensations according to
the structure of the end organs.

The sensibility of our skin appears to be mainly due
toa plexus of fine nerve-fibres, which end in free termi-
nations between the cells of the skin (rete mucosum).
There are also in some parts of the skin two sets of
minute corpuscles, which are called after their discoverers,
the first Vaterian, or more commonly Pacinian, cor-
puscles; the second, Meissner’s or Wagnev’s corpuscles.

8 THE ORGANS OF TOUCH.

The Pacinian corpuscles consist of a capsule formed
of several layers, one enveloping the other. The
undulating nerve-fibres, after several windings, enter
the capsule, which, indeed, seems to be nothing
more than a much-thickened end of the outer nerve-
coat. These corpuscles measure from 1:1 to 45mm.
They occur principally on the hands and feet, and
in the flexures of the joints, but occasionally also
elsewhere.

Fig. 9.—Pacinian corpuscle (after Leydig). Fig. 10.—Papilla from the surface of

a, Neurilemma ; b, nerve-fibril; c, cap- the hand, x 350 (aiter Kolliker). a,
sule; d, peculiar fibres; e, central Cone-like body; 0, nerve; c, end of
cylinder. nerve.

Meissner’s or Wagner’s corpuscles are cone-like or
ego-shaped bodies, in each of which a nerve termi-
nates, after several convolutions. ‘They are especially
numerous at the tips of the fingers, where there may
be as many as a hundred in a square line. They
occupy the papille (which, however, do not always
contain one), which give the surface of the hand its
peculiar striped appearance. ‘hey also occur, though
less numerously, elsewhere, as on the feet, breast, and
lips.

NERVES OF TOUCH. 9

It appears probable, however, that these are not
really the organs of touch, but rather, perhaps, guards
or protectors of the true and very sensitive organs
within. They are, no doubt, most numerous on the
‘more sensitive parts ofthe skin, such as the hands and
tongue, and the sense of touch is most acute where they
occur; but they appear to be absent in some places
where the sense of touch certainly exists, and they
are abundant again in the foot, which, though not
especially sensitive, is particularly exposed.

The sensation of pressure is intimately associated
with the hairs, which no doubt serve, at any rate in
some cases, for protection, but which, in Blix’s * opinion
are in man probably all organs of touch.

We have still indeed much to learn as to the
terminations of the nerves in the skin. It would seem
that some are connected with cells, while others termi-
nate in a free point. Merkel has suggested that tiose
which end in cells are the true nerves of touch, while
the free nerves record changes of temperature. Others,
perhaps with more probability, have supposed that the
_ free nerves convey merely a general and undifferen-
tiated sensation, while those which terminate in cells
give the specific impressions of pressure, heat, cold,
etc., any one of which may be intensified into pain.

However, this may be, blix * and, shortly afterwards,
Goldschneider f have made the interesting discovery
that we do not feel changes of pressure and of

* « Hixper. Beitr. zur Losung der Frage iiber die Specif. Energie der
Hautnerven,” Zevt. fiir Biologie, 1885, Blix’s previous papers in Upsala
Likan-forenings Férhandlingar, 1882, I have not seen.

t+ “‘ Monatschr. fiir prakt. Dermatologie.” 1884. ‘“ Neue Thatsachen
ii. die Hauptsinnesnerven,” Zool. Anz., 1885 und 1886,

10 SENSE OF TEMPERATURE.

temperature at the same points of the skin or by the
same nerve-ends. ‘The feeling of pressure seems to
be intimately associated with the hairs, which is not
the case with sensations of temperature. Even the
feelings of heat and cold are also separate. These
three sets of points, indeed, are so near together that
the separation had hitherto not been observed, espe-
cially as they are closely intermixed. ‘They have a
tendency, however, to arrange themselves in more or
less curved lines. Goldschneider experimented with
a fine point, which he passed over the skin, thus
testing it sometimes for pressure, sometimes with
a warm point for heat, sometimes with a cold point for

fairs WP

Fig. 11.—Portion of the skin of the back of the hand (after Goldschneider). The
centre figure represents the arrangement of the hairs; CP, the cold-points; WP.
the warmth-points.

cold. Moreover, if he raised the points thus determined

with a fine needle, and snipped off the fragment of the

skin, he found that the resulting sensation was quite
different in the three cases. If the point removed
was a “pressure-point ” the sensation was one for the
moment of pain; while the temperature-points gave
one respectively of heat or cold. ‘The terminations of
the temperature-nerves are, according to Goldschneider, -
much finer than those of the pressure-nerves, and they
are also fewer in number. He cut out from his own
skin a large number of sensitive points, but, while he
found that each corresponded to a nerve-end, he has
not been able to discover any difference at or in the

ORGANS OF TOUCH AMONG LOWER ANIMALS. 11

termination of the nerves corresponding to these differ-
ent sensations, though it may reasonably be expected
that such must exist.

The question has arisen whether there are separate
nerve-endings for pain, as apart from pressure, etc.; but
the observations of Blix and Goldschneider appear to
show that pain arises merely from the intensification of
other impressions, and that it does a reside in any
special organs.

SENSE OF ToucH AMONG THE LOWER ANIMALS.

Among the lower animals the outer skin is often
very sensitive, but we know scarcely anything as to the
minute structure of the organs of tactile perception.
In some cases they are, no doubt, very simple; but in
others it will probably be found that the apparent
simplicity is due to our deficient information and means
of investigation, rather than to any want of complexity
in the organs themselves.

In the Ceelenterata (zoophytes, etc.) certain sete,
especially on the tentacles and near the mouth, are
generally regarded as organs of touch.

In the epithelium of many of the lower animals, two
forms of cells may be detected. Some unmodified, or
indifferent, which form the gencral substance of the

epithelial layer; others more or less specialized, which
are seldom absolutely contiguous, but generally sepa-
rated by one or more of the indifferent cells.

In other cases, nerves may end abruptly at the
cuticle without the latter presenting, so far as our
present means of investigation have shown, any ap-
parent change; as, for instance, in the following

12 MEDUSZ.

figure of a part of the skin of a small worm
(Nereis).

Fig. 12.—Half of a cross section through the brain and hinder pair of eyes of Nereis
-cultrifera (after Carriere). 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 (9), but where the cuticle is unaltered; g, gelatinous body.
Among the Medusee (jelly-fishes), also, the supposed

tactile organs are ciliated cells (Fig. 13), which scarcely

differ from the other epithelial cells, but which ter-
minate externally in a cilia, and internally in a nerve-

fibril.

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meh se Fr }
a aH

Fig. 13.—Part of upper nerve-ring and tactile epithelium of Lizzia (after Hertwig).
a, Tactile epithelium; g, ganglionic cell; m7", upper nerve-ring.

In other cases, the tactile hairs scarcely differ from
those covering the general surface. Fig. 14 represents
part of the skin of a sea-anemone, the long cylinders
are nematocysts, or thread-cells—elastic sacs, in the

ANNELIDES.

13

interior of which lies coiled up a long filament, which

is often serrated at the end. Even a
very slight pressure causes this thread
to spring out, and these little darts,
which are present in immense numbers
in the skin of Hydrozoa (jelly-fish, etc.),
serve both as weapons of defence and
also to wound the small animals on
which they feed.

nz represents a nerve-cell, and it will
be seen that the hair in which it ter-
minates does not materially differ from
the rest.

In the Annelides, also, the general
surface of the integument (Fig. 15)

Fig. 14.—Diagram of
part of the skin of
a sea-anemone (Ac-
tinia); after Korot-
neff. dz, Glandular
cell; nz, nervous
cell,

presents tactile setz or ciliz, which are scattered over

Fig. 15.—Anterior part of body of Bohemilla comata (after Vejdovsky*). 1b, Tactile
hair; hp, hypoderm; c, cuticle; b, anterior part of brain; a, eye; ne, nerve-

fibrils; v, anterior blood-vessel.

the surface, and especially on the head.

* “Syst. und Morph. der Oligocheeten.”

In some cases

1884.

14 MOLLUSCA.

these sete are collected into special groups, either
situated in cup-shaped depressions of the skin, or on
more or less elevated papillae. Fig. 15 represents the
anterior part of the body of a small fresh-water worm
(Bohemilla), and shows clearly the small cuticular, and
the larger tactile, hairs. In other cases, asin the feelers
and cirri of the Alciopidz, there are short, shining,
ovoid rods, to the base of which runs a nervous fibril.
In the Mollusca, also, the surface of the skin is very
sensitive, and is generally provided with minute sete,
especially on the tentacles, or as in Lameliibranchiata
(mussels, etc.), on the edge of the mantle. Insome, the
snail for instance (Helix), the nerves, on approaching
the skin, have been ascertained to divide into a plexus

of fibrils.

Fig. 16.—Diagrammatic section through a papilla of touch of Onchidium (after Semper).
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;
m, nerve.

In Onchidium, a genus of slugs, Semper describes as
organs of touch (Fig. 16) certain slight elevations of the

MOLLUSCA. 5

skin caused by the cuticle being somewhat thickened.
Beneath these the epithelial cells are larger than usual ;
and under them, again, lies a cellular mass, the minute
structure of which he was not able to determine, but
which is connected with a nerve.

On the mantle of the Chitons are also certain
well-defined organs, probably of touch. They oecupy
pores in the shells, and resemble obconical or somewhat
dice-box shaped plugs of transparent, highly refracting

Fig. 17.—Diagram of the structure of the soft and some of the hard parts in the teg-

mentum 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; 7, rods of retina; n’, branches of
the optic nerve, perforating the capsule wall, and terminating in b’, db’, 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; é, nerve given off by one sense-organ to another, D’’.

tissue. The terminal knobs end in flat dises, which
show a series of concentric rings, as if composed of a
series of concentric layers or inverted cones fitted one
within the other.* Each one terminates in a nerve-

* Moseley, Quarterly Journal of Microscopical Soctety, 1885.
3

16 CRUSTACEA AND INSECTS.

fibre. They are of two distinct sizes, which Moseley
proposes to call macrcesthetes and micrcesthetes.

In many animals, as in ourselves, the outer skin is
soft and susceptible to external impressions. In Insects
and Crustacea on the contrary, the inner skin, or hypo-
derm, is covered with a more or less thick layer of
horny substance known as chitine; and, from the
nature of their chitinous integument, it naturally
follows that the sensations of insects, excepting that
of sight, are effected by means of variously modified
hairs. We know, however, so little, in the first place,
as to the real means by which animals, including
man, hear, smell, or taste, and, in the second, as to the
intimate structure of their minute organs, that we are
often in doubt, and there are still great differences of
opinion whether a given sense-hair serves for hearing,
smell, or touch.

The hairs of Arthropods belong to very different

Fig. 18.—Diagram of forms of hairs in insects. a, Ordinary surface hair; 6, plumose
natatory hair; c¢, hair of touch; d, auditory hair; e, olfactory hair; 7, taste hair ;
m, nerve hair.

categories, some of which we may perhaps distinguish
as follows :—
Those under which the chitinous integument is entire.
1. Ordinary surface hairs (Fig. 18, a).
2. Plumose natatory hairs (Fig. 18, b).
Those under which the chitinous integument is per-

SENSE-HAIRS. 1?

forated, and a special nerve-fibre runs to the base of the
hair. |
1. Hairs solid.

(1) Hairs attached stiffly; organs of touch
(Hig. 18, c).

(2) Hairs attached by means of a thin mem-
brane, sometimes plumose; organs of hear-
ing (Fig. 18, d).

2. Hairs hollow, and either open at the end, or
closed by an extremely delicate membrane.

(1) Hairs containing a continuation of the
nervous plasma ;
organs of smell
(Fig. 18, e).

(2) Hairs generally
very short, and
situated in the
mouth or on the
mouth part ; or-,
gans of taste
(Hie. 18, 7).

Each of these classes
is again subject to end-
less modifications, and
others will doubtless here-
after be discovered. The
sense-hairs are also often
more or less completely
sunk in the chitinous in- Fig. 19.—Part of the proboscis of a fly

(Musca); after Leydig. n, Nerve; g,
tegument. paneionic (es sama Ss, tactile hairs or

Fig. 19 shows some of a)
the tactile hairs on the proboscis of a fly (Musca), each
seated on a ganglion and connected with a nerve (7).

18 TACTILE HAIRS:

The tactile hairs—as, for instance, those on the upper
side of the proboscis of the fly—are delicate, hollow,
tapering, pointed organs, inserted on a chitinous ring,
and connected with a nerve which immediately below
the skin swells into a multicellular ganglion.

Fig. 20.—Right half of eighth segment of the body of the larva of a gnat (Corethra
plumicornis); after Graber. E, G, Ganglion; , 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’, termi-.
nation of skin-nerve; tb, plumose tactile hair; h, simple hair; ég, ganglion of
tactile hair; lm, longitudinal muscle. :

The terminations of the nerves and their connection
with the sensitive hairs are also beautifully shown in
some of the transparent water-insects. Fig. 20 repre-
sents part of one segment of the glassy larva of a gnat
(Corethra plumicornis), showing the tactile hairs (Fig.
20, h, tb), and the nerves connecting them with the

central ganglion (Fig. 20, HG).

CHAPTER IL.
THE SENSE OF TASTE.

WHILE the organs of touch are spread more or less over
the whole surface, and those of sight and of hearing
may be, and in fact are, situated in very different parts
of the body in different animals, the sense of taste is
naturally confined to the mouth or its immediate
neighbourhood.

In the case of Man, it resides especially in the tip,
the edges of the upper surface, and the back part of the
tongue, and (probably) the inferior portion of the soft
palate. The actual mode of termination of the nerves
of taste has, however, only recently been discovered.

Loven and Schwalbe detected, independently and
almost simultaneously, in the epithelium of the papille
of the tongue, many small budlike groups of cells (Fig.
21) which are probably connected with the ultimate
fibres of the glosso-pharyngeal nerves. These have
been supposed to be the special seats of the sense of
taste, and thence termed “taste-buds;” they are in
man shaped like a flask, in some other animals they are
more slender. In the dog, they are ‘072 of a millimeter
in length, and ‘03 in breadth. :

In the pig the number is estimated at 9500: in the
sheep, at 9600; in the rabbit, at 1500; in the cow, at

20 TASTE-ORGANS OF MAN.

39,000. Inman they almost touch each other on some
parts of the tongue, and their number is very great.

2g
SFE LE

Fig. 21.—Taste-Buds of the rabbit ty fe Engelmann in Stricker’s “ Handbook”), x 450.

The “taste-buds” consist of from fifteen to thirty
long narrow cells, arranged almost like a circular bundle.
Those on the outside lie in close contact with the walls
of the cavity. The cells appear to be of two kinds:

Fig. 22.—a, Isolated taste-cells from the mouth of rabbit; b, two cover-cells and a
taste-cell in their natural position (after Engelmann), x 600.

the outer ones do not differ markedly in appearance—
at least, with our present magnifying powers—from

ordinary epithelial cells, and have not been shown to
be connected with nerves. Those in the centre are

MAMMALIA—BIRDS—REPTILES. 21

more highly organized. Hach consists of an ellipsoidal
nucleus surrounded by a thin layer of protoplasm,
- continued downwards into a fine fibril, which sometimes
branches, and which—though this is not clear—probably
joins the nervous fibres. ‘'he upper process of the
protoplasm is a narrow cylinder, in some cases prolonged
at the end into a very delicate hair or rod.

Schwalbe thought he could distinguish in man and
the sheep, two kinds of taste-ceils—firstly, needle cells,
in which the cell appears to terminate in a narrow,
brilliant needle, abruptly cut off at the end; and,
secondly, staff cells, which are less numerous, shorter, of
uniform breadth, and without
anv terminating needle. It is
still unknown whether there are
different classes of taste-cells
for different tastes, and whether
one taste-bud can distinguish
more than one taste.

I know of no detailed de-
scription of the organs of taste
in birds and reptiles. In the
frog the taste-organs are not
flasklike, but are flat disks.
They occur in hundreds on the
tongue and soft palate. These
taste-disks are composed of Fig. _2i— Termmation of _ the
several forms of eells. Those showing the ramifications of

. the nerve-fibres and their con-
which are supposed to be espe- nection with the cells of taste
cially connected with the sense pd aie ens ae
of taste terminate in a fork, sometimes, though rarely,
of three prongs. The taste-organs of fishes are shaped

like beakers.

922 TASTE-ORGANS OF THE LOWER ANIMALS.

It will be observed that these structures give us no
help to realize in what actually consists the sense of
taste. We know that we possess it ourselves. We -
perceive that other animals can select, and appear to
enjoy, their food, and hence. we ascribe to them a
similar faculty. We know that in our own ease this
sense resides in the mouth, and we assume that it
must do so in other animals; we find in the mouth
certain structures, and we infer that to them is due
the sensation of taste. Hiven in our own case the
inferences are, perhaps, not very clear, and certainly the
facts, as yet known, aid us but little in framing any
definite idea of the process.

But if our knowledge is so imperfect in the case of
the higher animals, it becomes much more so in the
lower groups.

In the Mollusca, Annelida, and lower groups, we know ~
scarcely anything of the organ of taste, though we
ean hardly doubt that such
exists.

Medusz (jelly-fishes) are
very sensitive to any change
in the composition of the sea-
water ; for instance, they sink
below as soon as it begins to
rain. It is difficult, however,
ge ea ae Ee to say which sense is affected.

of the proboscis of Asterope can- In Asterope (a marine worm

dida, x 400 (after Greef). a, ‘ : a

Catile 2 ; ferminal “efoerre) belonging to the Alciopide),
longitudinal ‘muscle; ¢ trans- Greef has described, in the
skin of the proboscis, certain

peculiar club-shaped, ringed bodies, which taper into a
thread connected with a nucleated cell. These he

CRUSTACEA—INSECTS. yt

suspects to be ganglionic cells, and he suggests that the
organ is one of taste. .

Even in the Crustacea (crabs, lobsters, etc.), though
we can scarcely doubt that they possess the sense a
taste, no organs have been yet described to which it
can be with any confidence ascribed. Huxley, for
instance, in his work on the Crayfish,* says, “It is
probable that the crayfish possesses something ana-
logous to taste, and a very likely seat for the organ of
this function is in the upper lip and the metastoma, but
if the organ exists it possesses no structural peculiarities
by which it can be identified.”

As regards insects, the possession of the sense of taste
cannot be questioned, though, except perhaps in many
Hymenoptera and certain phytophagous insects, it may
not be of great importance. No one who has ever
watched a bee or a wasp can entertain the slightest
doubt on the subject. It is, again, probably by taste
that caterpillars recognize their food-plant. Moreover,
this is partly the effect of individual experience, for,
when first hatched, caterpillars will often eat leaves
which they would not touch when they are older, and
have become accustomed to a particular kind of food.
Special experiments, moreover, have been made by
various entomologists, particularly by Forel and Will.
Forel mixed morphine aud strychnine with some honey,

* «The Crayfish : an Introduction to the Study of Zoology.”

+ A remarkable case is afforded by those species in which the food of
the larva and perfect insect is different, so that the mother has to select
and find for her offspring food which she would not care to touch her-
self. ‘Thus while butterflies and moths themselves feed on honey, each
species selects some particular food-plant for the larve. Again, flies,
which also enjoy honey themselves, lay their eggs on putrid meat and
other decaying animal substances,

24 SENSE OF TASTE IN INSECTS.

which he offered to his ants. Their antenne gave them
no warning. The smell of .the honey attracted them,
and they began to feed; but the moment the honey
touched their lips, they perceived the fraud. Will tried
wasps with alum, placing it where they had been accus-
tomed to be fed with sugar. They fell into the trap,
and ate some, but soon found out their error, and began
assiduously rubbing their mouth parts to take away the
taste.

Will found that glycerine, even if mixed with a large
proportion of honey, was avoided; and to quinine they
had a great objection. If the distasteful substance is
inodorous and mixed in honey, the ant or bee com-
mences to feed unsuspiciously, and finds out the trick
played on her more or less quickly according to the
proportion of the substance and the bitterness or
strength of its taste.

The delicacy of taste is, doubtless, greater in bees
and ants than in omnivorous flies or in carnivorous
insects. At the same time, the sense of taste in ants is
far from perfect, and they cannot always distinguish in-
jurious substances. Forel found that if he mixed
phosphorus in their honey, they swallowed it unsus-
pectingly, and were made very unwell. Some workers,
he says,” “de Formica pratensis se gorzérent de miel au
phosphore que je leur donnai. Apres cela elles
demeureérent pendant de nombreuses heures immobiles,
les mandibules écartées, la bouche ouverte, avec lair
tres obsédées. Celles qui en avaient le plus mangé
périrent, les autres guérirent peu a peu.” It cannot,
then, be doubted that insects possess a sense of taste,
the seat of it can hardly be elsewhere than in the

*“ Receuil Zool. Suisse.” 1887. va)

ORGANS OF TASTE IN INSECTS. 25

mouth or its immediate neighbourhood; and in all the
orders of insects there are found on the tongue, the
maxille, and in the mouth, certain minute pits which
are probably the organs of taste. In each pit is a
minute hair, or rod, which is probably perforated at
the end. On this point there is, indeed, some dif-
ference of opinion. Will, for instance, maintains
that to convey the sense of taste the food must come
into direct contact with the termination of the nerve
of taste, so that those hairs, or bristles, on the mouth
parts which present no perforation cannot be regarded
as true taste-organs, and probably serve rather as
guards. Forel, on the contrary, considers this as an
error. He observes, with justice, that the secretions
are able to pass through the chitinous membrane
which terminates the excretory canals of the glandular
cells, and he maintains that the chitin is so thin
and delicate—as well on the surface of the taste cones
and hairs as on the olfactory hairs and plates of the
antennze of bees and other insects—that endosmosis
through this fine membrane may sufficiently explain
the sensation.

In 1860 Meinert* described, on the maxille and
tongue of ants, a series of chitinous canals, connected
with ganglion cells, and through them with the nerves,
and suggested—though with a note of interrogation-—

that they might be the organs of taste. Forel, in 1874,
confirmed these observations of Meinert’s, and described,
at the point of the tongue of Formica pratensis, a series
of seven such chitinous tubes. In the following year
Wolff published his work, “Das Riechorgan der Biene,”
which contains a number of valuable observations,

* «Bid. til. de Danske Myrers Natur Hist.” 1860.

26 THE BEE.

though I am unable altogether to concur in his con-
clusions. He described a group of minute pits at the
base of the tongue of the bee, and considered them
as the organs of smell. It seems to me, however, more
probable that they serve as organs of taste. Forel *
also is disposed to regard these as constituting, perliaps,
the most important part of the organ of taste, but con-
siders that this sense resides also in eertain organs
scattered over the tongue and the maxille. Will
regards the maxille and tongue as the only organs of

Fig 25.—Taste-organ of the bee (after Wolff). 2B, Horny ridge; R, R, sensory pits,
C, C, skin of the mouth ; Z, muscular fibres; A, A, muscular fibres; S, 8’, abe
d ef, section of skin of esophagus.

taste in the bee. He maintains that the organs of
Wolff are deficient in the first requisite of an organ of
taste, for that there is no orifice through which the food
could directly enter into relation with the nerve.

No doubt, moreover, the taste-organs on the
tongue and maxille might be of themselves suffi-
cient, so that a@ priort we need not seek for any
others. At the same time, as to the existence of the

* « Sensations des Insectes,” Rad Zool, Suisse, 1887. Kraeps
also regards them as the organ of smell.
t Will, “ Das Geschmacksorgan der Insekten,” Zett, fiir Zool., 1855.

HYMENOPTERA. oF

organs described by Wolff there is no doubt, and
their position certainly seems to indicate that they
are organs of taste. Moreover, we are not, I think,
sufficiently acquainted either with the essential
requisites of an organ of taste, on the one hand, or, on
the other, with the minute structure of these organs, to
feel justified in concluding that this is impossible. It
must be remembered that these pits are very minute,
being only from ‘008 to ‘006 of a millimetre in diameter,
so that it is hazardous to assert that they are certainly
imperforate, while even if they are,
this would not necessarily prove
that they cannot be organs of taste.

Fig. 26 shows three of Wolff's
cups, each with a central hair, a
chitinous ring, and a double gan-
glionic swelling terminating in a
nerve-fibre, magnified 500 times. ;

An additional reason for sup- Swain Goat cae sah

central hair, a chitinous

posing that the Wolffian pits ate ring, and a double gangli-

onic swelling terminating

really sense-organs arises from the in a nerve-fibre, x 500
fact that they are fewest in those and faites - a
insects which we may reasonably 9° 8" ™*¥°
suppose to have the sense of taste least developed,
and increase in number where, on other grounds, we
may fairly regard it as being probably more highly
developed. Thus the Chalcidide have often only one
or two; the Evaneade, seven; the Proctotrupide,
fifteen; the Tenthredos, twelve to twenty-four; the
common wasp, twenty : some of the great tropical wasps,
forty; while in the hive bee, the drone has fifty, the
queen about one hundred, and the worker rather more
still, say one hundred and ten.

28 HUMBLE BEE—WASP.

Kraepelin has described at the end of the proboscis
in the humble bee (Bombus), besides the hairs of touch,
certain peculiar club-shaped hairs, which he believed
were perforated at the end, and which he considered to
be taste-hairs; and Haller has ascribed the same
function to some very similar hairs which he found on
the under lip of the Hydrachna.

Fig. 28.—Section through a taste-
cup (after Will). S&, Support-
ing cone; JV, nerve; SZ, sense-

~cell.

Fig. 27.—Under side of left maxilla of
Vespa (after Will). Gm, Taste-cups,
Shm, protecting hairs; 70, tactile hairs ;
Mt, base of maxillary palpus.

Fig. 27 represents the under side of the left maxilla of
a wasp (Vespa vulgaris), after Will, magnified 55 times.
Gm are the taste-cups; Shm, the protecting hairs ;
Tb, the tactile hairs.

Fig. 28 represents a section through one of the taste-
cups, Sk is the taste-cone contained in the cup; it is
perforated and continuous at the base with a nerve-fibre,

FLY. 29

Similarly, in the wonderfully beautiful and complex
proboscis of the hive bee there is, between each of the
trachea-like ducts, a row of minute pits (Fig. 29, Gs),
with a central papilla, which have been described by
Leydig, Meinert, Lowne, Kraepelin, and others, and
are probably organs of taste.

Kraepelin* distinguishes four kinds of hairs on the
proboscis of the fly :

1. Ordinary hairs, which are not hollow, and do not
stand in connection with a nerve.

2. Hairs of touch. These are
principally situated on the upper
side. They are delicate, hollow,
pointed organs, situated on a ring
of the integument, and connected
with a nerve. |

3. Glandular hairs. These are
larger than the former, and the
chitinous ring 1s sometimes so much
developed as to form a short cylin-
der surrounding the base of the Fig. 29—Tip of the probos-
hair. The principal characteristic x nao. ee
a P ladle; Gs, taste-hairs ;
is, however, that the hair presents sh, “guard-hairs; Hb,
alone one surface a deep furrow, ae Oka
and is connected at the base with a cellular organ.
Kraepelin therefore considers that this is a gland, and
that the secretion passes outwards along the furrow.
Kunckel and Gazagnaire, however, regard these also as
sense-hairs. ‘The supposed gland they consider to be
a ganglion.

4, ‘Taste-organs (Fig. 30). These lie in a row between

* Kraepelin, “Zur Anat. und Phys, des Riissels von Musca,” Zeit.
fur Wiss. Zool., 1883.

30 FLY.

the trachea-like channels, and correspond to the similar
organs in the bee (Fig. 29, Gs). Hach of these resembles
a double circle, which scarcely projects, if at all, beyond
the general surface, and which he regards as a
metamorphosed, hollow, perforated hair. At the base
of each organ is a nerve, which at some little distance
forms a multicellular ganglion, and the
sheath of which, immediately below the
skin, forms a delicate and short, but well-
marked, chitinous, cylinder.

It may also be observed, at any rate in
most insects, that while they are feeding
the palpi hang down motionless, and evi-
dently take no part in the operation.

In reference to the sense of taste, I may
also mention that an additional complexity
arises from the fact that many insects
possess more than one kind of salivary
gland, and it is possible, as Wolff sug-
re gests,* that the secretions may have dif-
Fig. 30. Organ ferent properties. In addition to this,

of taste of fy Wolff thinks he has proved that the

(Musca vomi-

toria); after 2 ete : .
ope Meh os 3 character of the secretion differs at differ

Nerve; 99,ean- ent ages; that for many days after the

glion; az, axe-
Crnecteyig, bee has arrived at its imago condition,
der: gk, termi- the glands are still imperfect and gradually
increase to their full size. In old bees,
again, according to him, the secretion diminishes in
quantity. This, perhaps, throws some light on the
division of labour. Forel has observed among ants
that they remain for some days engaged in indoor

Pee

* “Das Riechorgan der Biene.”

INDIVIDUAL DIFFERENCES. 31

duties, and do not leave the nest till some time after
they have arrived at maturity.

I have noticed, also, that some individuals seem to
possess a finer sense of taste than others, and some light
seems to be thrown on this difference by the fact that
the number of the taste-pits is not the same in all indi-
viduals. Thus Will observed that the number on the
tongue of Lasius flavus (our common yellow ant) varies
from twenty to twenty-four, and in Atta from forty to
fifty-two. The number of pits on the maxille is subject
to still greater variations, and is not even always the
same on the two sides of the same insect.

On the whole, then, we may conclude that the organs
of taste in insects are certain modified hairs situated
either in the mouth itself or on the urgans immediately
surrounding it.

CHAPTER IIL
THE SENSE OF SMELL.

THE organ of smell is, in vertebrate animals, embedded in
the mucous membrane of the nostrils, and in mammalia
can generally be distinguished by its yellow or brownish
colour. In birds, on the contrary, it presents hardly
any peculiarity to the naked eye. For our knowledge
of the minuter structure we are mainly indebted to
Max Schultze. The cylindrical epithelial cells in the
olfactory organs of man (Fig. 31) terminate in broad flat
ends. Between them are rud-like filaments, which are
supposed to expand into a ganglionic cell, terminating
in a nerve-fibre. Schultze terms these olfactory cells.

In other cases, as in birds, Amphibia (Fig. 32), etc.,
the olfactory cells terminate in fine ciliz, or olfactory
hairs, either one or many to each cell. These hairs
are sometimes motionless, sometimes have a slight
movement of their own. It is obvious that no one from
the structure alone could have predicated the function ;
nor can we, I think, form to ourselves any satisfactory
conception how such a structure conveys the impression
of smell, or in what consist the differences between
different odours.

If, then, we know really so little as to the mode, or
organs, by which the sense of smell is induced among

PROTOZOA AND CCRLENTERATA. oo

the higher animals, we cannot wonder that in the
lower groups our knowledge is still less.

In the Protozoa and Coelenterata no organs have yet
been met with to which this function can with any
confidence be ascribed.

"9 60909
00.90 ° S60

0%’, 6°
Oo" o

a
oo

2

co
oe 8

5)
ae: °

Fig. 31.—Epithelial
and (B) olfactory

pee rom Fig. 32.—Cells from the olfactory
aa after region of a proteus (after Stricker).
chultze). a, Epithelial cells; 6, the apparent

z processes; ¢, olfactory cells. A,
Ciliz.

Meyer has described,* in Polyophthalmus (a small
marine worm), on each side of the head, two ciliated
organs (Fig. 33), which have been supposed to be organs
of smell. These had been already mentioned by

* “Zur. Anat. und Hist. von Polyophthalmus,” Arch. fiir Mic.
Anat., 1882.

34 WORMS— MOLLUSCA.

De Quatrefages, who compared them with the ciliated
wheels of Rotifers, and thought that they produced
currents in the water, thus urging microscopic alge,
infusoria, etc., to the mouth of the worm. Meyer, on
the contrary, with more probability, regards them
as olfactory organs. ‘They are slight depressions
(Fig. 33) in the general surface, lined with peculiar
long ciliz, supplied with a large nerve coming from

Fig. 33.—Section through the head segment of Polyophthalmus, x 300 (after Meyer).
Imd, muscle; bo, cup-shaped organ; cu, cuticle; hp, hypoderm; Jmd, longitu-
dinal dorsal muscle: n, peripheral nerve; cz, commissure of brain; mb, mem-
brane ; pgn, pigment-cells ; hpdz, unicellular glands in the hypoderm ; gn, brain ;
k, nuclei in the brain.

the cerebral ganglion gn. Similar pits occur in many
other Annelida. They differ in number; Polyoph-
thalmus having only a pair, the Capitellidee several.
In the Mollusca, the hinder pair of tentacles have
been supposed by some to serve as olfactory organs.
In the cuttle-fish (Cephalopoda) there are certain pits,
at the base of which is a papilla, supplied with a nerve,
which is perhaps olfactory.* The true function of the

* Leydig, “ Histologie.”

INSECTS—SEAT OF THE SENSE OF SMELL. 395

organs described by Hancock in Gasteropods, and by
Leuckart in Pteropods, as olfactory, seems very doubtful.

As regards the seat of the sense of smell in insects,
there have been four principal theories. It has been
supposed to reside—(1) In the spiracles, or breathing
holes; (2) in the neighbourhood of the mouth; (8) in
the antenne; (4) in different parts of the body. The
history of the question has been well given byKraepelin
in an admirable memoir, “ Ueber die Geruchsorgane
der Gliederthiere.” *

Sulzer, in 1761,} suggested that the organ of smell
was probably to be found in the neighbourhood of the
spiracles, or breathing-holes. It is hardly necessary to
observe that insects do not breath as we do, through
their mouths, but through a series of orifices along the
sides, leading into trachez, or air-tubes, which ramify
throughout the body; so that the blood is aerated, not
in one special organ, but throughout its course. Now,
it is important that a more or less continuous current
of air should pass over the surface of the organ of
smell, as it is in this manner brought in contact with
the odoriferous particles. In man and the other air-
breathing vertebrates, the combination of the entrance
to the lungs with the nose and mouth offers great
advantages. ‘The olfactory organ is brought close to
the mouth, where it is especially useful in the exami-
nation of food; while the continuous current of air
necessary to respiration is utilized in the production
of sound, on the one hand, and in bringing odoriferous
particles to the organ of smell, on the other.

* Separat Abdruck aus dem Osterprogramm der Realschule des
Johanneum.” 1883.
+ “Geschichte der Insekten.”

36 DIFFERENT THEORIES AS TO

In insects the separation of the mouth from the
respiratory orifices is, in this respect, a manifest dis-
advantage. Still, it was not unnatural to look for the
organ of smell in the neighbourhood of the spiracles,
Sulzer’s view was supported by Von Reimarus, Baster,
Dameril, Schelvir, and especially by Lehmann,* who
lays it down asa general proposition that every organ of
smell is to be sought near the orifices through which
animals breathe: “ Omnibus olfactus organon in lis
locis queerendum est, per quos inspirent.”

The most careful observations, however, have failed
to detect in the neighbourhood of the spiracles any
special supply of nerves, or any organ which could be
supposed to serve for the perception of odors, and I
believe this view may be said to be now generally
abandoned. t

Treviranus { suggested that the organ of smell was
situated in the mouth, and he has been followed by
Newport, Wolff, Kirby and Spence, and Graber. The
descriptions they have given may be accepted as
correct, but the organs they describe in the mouth
itself are rather, I think, to be ascribed to the sense
of taste than to that of smell.

Lyonnet, Bonsdorff, Marcel de Serres, Newport, and
others, believed that the sense of smell resides in the

* Lehmann published three memoirs on the subject: “ De Sensibus
Externis Animalium Exsanguium,” 1798; ‘‘De Antennis Insectcrum

Dissertatio,” 1799; and “De Antennis Insectorum Dissertatio Pos-
terior,’ 1800.

+ Joseph, indeed (“ Bericht der 50 Vers. Deutscher Nat. und Aerzte.
Miinchen,” 1877), supported this view in a short communication, and
has promised fuller details. These, however, have not, I believe, yet
appeared.

{ “Ueber das Saugen und das Geruchsorgan der Insekten,” Ann.
der Wetter Ges., 1812.

THE SEAT OF THE SENSE OF SMELL. 37

palpi, although the experiments of Perris, Plateau,
Forel, and others, have conclusively proved that it
is not situated exclusively in them.

The credit has been ascribed to Réaumur of having
been the first to suggest that the sense of smell is
seated in the antenne. This view has been adopted
by Lesser, Roesel, Lyonnet, Bonnet, Sulzer, Latreille,
Burmeister, Lefevre, Erichson, Dugés, Perris, Dufour,
‘Slater, Vogt, Forel, Lowne, Hauser, Kraepelin, Schie-
menz, and other observers, and my own observations
lead me to the same conclusion.

Many entomologists, indeed, including Scarpa, Schnei-
der, Bolkhausen, Bonsdorff, Carus, Strauss-Durckheim,
Oken, Kirby and Spence, Newport, Landois, Hicks,
Wolff, and Graber, have considered that the antennz
serve as ears. ‘hese two views are, however, not
irreconcileable, and the truth seems to be that, while
organs of smell and of hearing, when present, may be
both situated in the antenne, they are not in all cases
confined to them.

Comparetti* seems to have been the first to suggest
that the organ of smell might not be seated in the
same part of the body in all insects; he suggested the
antenne in certain beetles (Lamellicornia), the pro-
boseis in butterflies and moths (Lepidoptera), and
certain frontal cellules (the existence of which has,
however, not been confirmed) in locusts, ete. (Orthop-
tera), as the probable seats.

The real manner in which odors are perceived, and
the structure of the olfactory organs, is still so little
understood, that experiments are perhaps more con-
clusive than anatomy.

* “De aure interna comparata-Patavii.” 1789.

38 EXPERIMENTS.

The oldest experiments of importance are those of
Lehmann. He bored holes through bottles, and then
inserted into them the abdomen of various insects, fillmg
up the interspace with wax, and leaving the head and
thorax outside. He then introduced into the bottle
various powerful odors, such as burnt feathers, assafoe-
tida, burnt sulphur, etc., and as these caused obvious
movements of the body, he concluded that the insects
perceived the smell by the membrane surrounding the
trachez. ‘The facts have been verified by subsequent
observers, and are themselves doubtless correct. They
do not, however, prove Lehmann’s case, for similar fumes
would, as Duges and Perris justly observe, produce an
irritation in our throat, where there is certainly no
sense of smell. On the other hand, when substances
which have no such irritating properties are used, as,
for instance, honey in the case of a bee, decaying meat
with a carrion-eating beetle (Silpha), and so on, no re-
action has been perceived. On the whole, experiments
lend no countenance to Sulzer’s theory (see p- 3d),
and, in the absence also of any anatomical evidence
in its support, it has, I believe, now no advocates.

I pass, then, to the second theory—that which
considers that the organ of smell is situated in the
mouth parts, either in the mouth itself according to
some authors, or the palpi according to others. We
have, I think, no clear evidence that the mouth itself
possesses any organ of sme!l. Huber, however, observed
that while, if he brought close to the mouth of bees
substances which were repulsive, or others which
were acceptable to them, such as honey, they were evi-
dently affected; this was, on the other hand, no longer
the case if the mouth parts were stopped up with paste.

EXPERIMENTS WITH DINETUS. 39

Perris, on the contrary, found that even when the
whole of the mouth parts were enclosed in gum, insects
still retained the power of smell. ‘These observations
have been entirely confirmed by Forel and other
observers. The explanation, I believe, is that Com-
paretti was right, and that the sense of scent 1s not
confined to one part of the body; that, while it is pos-
sessed by the palpi, it is not confined to them.

It has long been observed that insects use their
antennee to examine and test their food. This is clearly
not an act of hearing; nor has any one suggested that
the antenne are organs of sight or taste. It is obviously

“more than mere touch—indeed, they do not need to
come into actual contact—and is, therefore, probably
that of smell.

This conclusion has been confirmed by many experi-
meuts. Among those of the older observers some of the
most important were made by Perris.* In Dinetus, a
genus of the solitary wasps, the female, when absent in
search of prey, covers over the orifice to her nest with a
little sand. Perris selected two nests, and while the
wasps were absent he disturbed the surface round one
nest with a piece of stick, and laid his hand (which was
rather warm) over the other. ‘The first Dinetus was a
little disturbed. She ran about, rapidiy vibrating her
antenne, and was, perhaps, rather longer than usual in
finding the entrance, but lost very little time. The

other, he says, “Se trouva de prime abord, beaucoup
plus embarrassé: ma main, dont |’état de moiteur avait
rendu les émanations beaucoup plus actives, avait
laissé sur le sable une odeur qui semblait |’étonner, et
* “Sur le siege de l’odorat dans les articulés,” Ann. Sct. Nat.,

1850.
+

40 EXPERIMENTS WITH HYDATICUS.

qu'il cherchait & reconnaitre: car lorsqu’ll arrivat 4
Vendroit que ma main avait couvert, il ralentissait sa
marche, et ses antennes palpaient rapidement le sable.
Le pauvre insecte sépuisait en marches et contre-
marches; il passait par dessus son nid sans s’en doutert ;
il creusait ca et la avec ses pattes de petites fosses, dans
lesquelles il plongeait ses antennes pour explorer les
couches inférieures; il s’arrétait pour brosser ses
autennes, comme on se frotte les yeux quand on se
sent ébloui: rien n’y faisait. Découragé, il prit son
vol; mais il revint quelques instants apres et recom-
menga ses recherches. Cette fois, soit qu'il fit mieux
disposé et que les antennes qui étaient évidemment
Vagent explorateur, fussent plus perspicaces, soit plutdét
que le soleil qui était ardent etit fait évaporer les
émanations de ma main, il parvint retrouver son nid,
mais il y mit bien du temps et de Ja patience.”

Perris also repeated Lehmann’s experiment, only
that he inserted the head of the insects into the bottles
instead of the body; he then satisfied himself that
they perceived odors, and hence concluded that the
sense of smell resides in the head, partly in the antenne,
and partly in the palpi.

Newport, on the contrary, maintained that the
antennee possess no sense of smell. He experimented
on a water-beetle, Hydaticus cinereus, which, he says, “I
had purposely confined for three days without food in
a cup about half filled with water, and, at the expiration
of that time, attached a small piece of raw flesh to the
end of a wire, and carried it several times along the
sides of the insect, particularly near the spiracles, where
it was suffered to remain for a short time. The insect,
however, did not appear to perceive it, but during the

ichd
gh ee

EXPERIMENTS WITH SILPHA. 4]

whole time remained in the water perfectly undisturbed.
The flesh was then carried very near to one of the
antenne, but without exciting the slightest motion in
that organ, while tne insect began to move its palpi
very briskly, as if it detected the presence of something;
but continued, in other respects, motionless as before.
The flesh was then brought in direct contact with the
antenne, and the insect immediately withdrew them as
if annoyed, as in the experiment with the Silpha. It
was then carried exactly in front, and at about the
distance of an inch. ‘The palpi were instantly in rapid
motion, and the creature, darting forward, seized the
“flesh, and began to devour it most voraciously. The
following day the experiment was repeated several
times, and with precisely the same result; but on this
occasion the antenne were so repeatedly touched with
the flesh, that the annoyed insect kept them at last
‘beneath the sides of the thorax. Hence I think it
must appear that, from there being no alterations in
the motions of the insect when the food was held
near the sides of its body, the sense of smelling does
not reside in the spiracles, nor, for like reasons, in
the antenne; while, from the motion of the palpi
and the avidity with which the insect darted upon the
- feod when held in front of it, it seems but fair to con-
clude that the sense of smelling must serenity reside
in the head, as above suggested.” * .

Again, he took a Silpha (one of the carrion-eating
beetles), and, “placing it in a glass, attached a
small piece of flesh within half an inch of it. The
antennee, as is usual with these insects, continued to

* Newport, “On the Antenne of Insects,” Transactions of the Ento-
mological Society, 1837-1840.

42 EXPERIMENTS WITH SILPHA.

be moved about on either side, but with nothing
remarkable in their motions, while the head of the
insect was a little elevated and carried forwards, as if it
perceived the flesh, and the palpi were in rapid vibra-
tory motion. It soon approached very near to the food,
and at length touched it three or four times with the
antenne, but each time suddenly withdrew them as if
they had fallen unexpectedly on something obnoxious,
the palpi during the whole time continuing their motion.
The insect at length reached the food, and, after having
touched it once or twice with the extremities of the
palpi, their motion ceased, and it commenced feeding,
while the antenne were occasionally in motion as
before.” It would certainly seem, therefore, that in
these insects, at any rate, the sense of smell resides
principally in the palpi.

Newport made certain other experiments on the
powers of hearing of insects, which I shall mention in
the next chapter, and he concludes, “These facts,
connected, with the previous experiments, have con-
vinced me that the antennz in all insects are the
auditory organs, whatever may be their particular
structure, and that, however this is varied, it 1s appro-
priated to the perception and transmission of sound.”

Newport was an excellent observer and profound
entomologist, and I see no reason to doubt the correct-
ness of his observations; nor, indeed, of his inferences,
so long as we confine them to the species on which the
observations were made. ‘bey may prove that some
insects possess no sense of smell, or that, at any rate,
it does not reside in the antenne. On the other
hand, they cannot disprove the positive results obtained
by other observers, that in other species the opposite is

EXPERIMENTS WITH STAG-BEETLE, ANTS. 43

the case, and that in them the sense of smell does
reside in the antenne.

That the stag-beetle can smell seems clearly proved,
but Landois found* that, after the removal of the
terminal plates of the antenne, the insect still possessed
this faculty, whence he concluded that the sense of
smell must reside in some other part of the body, and
that the antennz probably serve as organs of hearing.
This does not, however, prove that the sense of smell
does not reside partly in the antenne.

Forel removed the palpi and mouth parts of a wasp,
and she appeared to perceive the presence of honey as

well as before.

I myself took a large ant (formica ligniperda), and
tethered her on a board by a thread. When she was
quite quiet, I tried her with tuning-forks; but they
did not disturb her in the least. I then approached the
feather of a pen very quietly, so as almost to touch
first one and then the other of the antenne, which,
however, did not move. I then dipped the pen in
essence of musk and did the same; the antenna was
slowly retracted and drawn quite back. I then repeated
the same with the other antenna. I was, of course,
careful not to touch the antenne. I have repeated
this experiment with other substances with several
ants, and with the same results. Perris also made the
same experiments with the palpi, and with the same

result; but if the palpi were removed, the rest of the
mouth gave no indications of perceiving odours.

Graber ¢ also has made a number of experiments, and

* “Das Gehororgan des Hirschkéfers,” Arch. fiir. Mic. Anat., 1868.
tf “Vergl. Grundversuche iiber die Wirkung und die Aufnahme-
stellen chemischer Reize bei den Thieren,” Biol. Centralblatt, 1885.

44 SEAT OF THE SENSE OF SMELL

found that in some cases (though by no means in all),
insects which had been deprived of their antenne still
appeared to possess the sense of smell. But if, as we
have, I think, good reason to suppose, the power of
smell resides partly in the palpi, this would naturally
be the case. |

He also tested a beetle, Silpha thoracica, with oil of
rosemary and assafcetida. It showed its perception
by a movement in half a second to a second in the
ease of the oil of rosemary, and rather longer—one
- second to two seconds—in the case of the assafcetida.
He then deprived it of its antenne, after which
it showed its perception of the oil of rosemary in
three seconds on an average of eleven trials; while in
no case did it show any indication of perceiving the
assafcetida even in sixty seconds.

This would seem to indicate a further complication—
not only that both the antenne and the palpi may
possess the sense of smell, but also that certain odours
may be perceived by the former, and others by the latter.

Graber questions some of the experiments which
seemed to me * to demonstrate the existence of a sense
of smell in ants.T

* « Ants, Bees, and Wasps.”

t He says, ‘Da Lubbock noch hinzufiigt, dass keiner, der das
Benehmen der Ameisen unter diesen Umstanden beobachten wiirde,
den geringsten Zweifel an ihrem Geruchsvermégen haben kéunnte,
wahlte ich auch diese Methode, um zu erforschen, wie sich etwa der
Fihler beraubte Ameisen verhalten wiirden. Ich war nicht wenig
iiberrascht zu finden, dass auch diese (es handelt sich um Formica
rufa) vor dem Riechobjekt umkehrten. Um ganz sicher zu gehen,
versuchte ich’s aber noch mit dem gleichen Arrangement aber mit
Weglassung des Riechstoffes, und siche da! sie kehrten auch jetzt noch
um! Bei genauerer Beobachtung der von einer Ameise vom Anfang
an auf dem Papiersteg zuriickgelegten Strecke stellte sich auch bald

—— 314)"

PARTLY IN THE PALPIL. 45

I fastened a strip of paper in the air by means of two
pins, suspended over it a camel’s-hair brush containing
scent, and then put an ant at one end. She ran forward,
but stopped dead short when she came to the scented
brush. Graber suggests that she did so from
giddiness, but I am satisfied that this is not so.
Ants which habitually climb trees are not likely to
be affected by any such sensation. In my experi-
ments, whether the bridge was high or low, broad or
narrow, made no difference to them. Moreover, in
each case they stopped exactly when they came to the
scented pencil. Again, Graber has not observed that
I expressly stated that “after passing two or three
times, they took no further notice of the scent;”
nor did they notice the camel’ s-hair pencil unless it
was scented.

As regards flies (Musca), Forel removed the wings
from some bluebottle flies and placed them near a
decaying mole. They immediately walked to it, and
began licking it and laying eggs. He then took them
away and removed the antenna, after which, even
when placed close to the mole, they did not appear to
perceive it.

Plateau also * put some food of which cockroaches
are fond, on a table, and surrounded it with a low

heraus dass es sich bei dem gewissen Umkehren lediglich um ein
versuchsweises Abschreiten oder Ausprobiren des unbekannten Weges
handelte, oder das sich die Ameisen ahnlich benehmen wie wir selbst,
wenn wir etwa auf einem schwanken Brette eine tiefe Gebirgskluit
tiberschreiten sollen.”

Graber’s observation is, I doubt not, quite correct; but his inference
is not, I think, well founded, nor was his experiment the same as
mine.

# Bull. de la Soc. Ent. Belgique, 1876.

46 SEAT OF SMELL PARTLY IN ANTENNAL-

circular wall of cardbuard. He then put some cock-
roaches on the table: they evidently scented the food,
and made straight for it. He then removed their
antennee, after which, as long as they could not see the
food, they failed to find it, even though they wandered
about quite close to it.

On the whole, then, the experiments which have
been made seem clearly to prove that in insects the
sense of smell resides partly in the antennz and partly
in the palpi. This distribution would be manifestly
advantageous. ‘The palpi are more suited for the ex-
amination of food; while the antennz are more con-
veniently situated for the perception of more distant
objects.

We will now glance at the antenne and palpi
themselves, and consider briefly the structures which
are supposed to give the sensation of smell. For
this three conditions are requisite: (1) an appropriate
nerve; (2) free access to air; and perhaps, though
this is not so clear, (3) a fluid which can dissolve the
odoriferous substance.

The olfactory organ in Vertebrata consists, as already
mentioned, of a mucous membrane containing (1)
cylindrical epithelial cells, with a broad, flat termination
at the free end; and (2) of rod-like filaments which,
some little distance below the surface, swell out into
a nut-shaped expansion, and then contract again into a
fine thread, which is probably continuous with the
fibrils of the olfactory nerve.

In Insects and Crustacea the conditions are different.
The cellular “underskin,” or hypoderm, secretes a hard,
horny envelope, and the terminations of the olfac-
tory nerves are enclosed in a horny tube with a

THE ORGANS OF SMELL. 47

terminal perforation, or project as free threads.
They differ, again, between themselves, Insects being
as a general rule aerial, and Crustacea aquatic.
Erichson* has the merit of having been the first
to support this theory by anatomical examination.
Newport had previously mentioned the existence in
many insects of certain pits, or “pores,” closed by a
delicate membrane, and which he regarded as the seat
of hearing. Erichson extended his observations, and
suggested that the pits were rather to be regarded as
organs of smell. His descriptions were confirmed by

Fig. 34.—Antenna of Pontella Bavrdti (Lubbock).

Burmeister, who, moreover, detected in some of these
“pits” the presence of a small knob, or hair.

In 18538 I called special attention to the antennez
of certain Crustacea, distinguishing five kinds of
hairs—(1) short, downy hairs; (2) plumose hairs; (8)
cylindrical, tapering hairs; (4) flattened, lanceolate
hairs; (5) wrinkled hairs—and pointed out that they

were by no means scattered indiscriminately, but
arranged in definite situations, indicating special
functions. The two last I was disposed to regard
as sense-organs. ‘The above is a figure of the right
male antenna of Pontella Bairdii, one of the Cope-

* “ De Fabrica et usu Antennarum in Insectis.” 1847.

48 LEYDIG’S OLFACTORY CONES.

poda, from one of my memoirs in that group,* and
shows the curious clasping organ.

Leydig, in his beautiful work on the Daphnide, and
more fully-in a special memoir on the subject,f de-
scribed certain organs which had been also mentioned
by La Vallette. I give below his figure of the
terminal segments of one of the smaller antenne of
the water-woodlouse (Asellus aquaticus) magnified 500
times. It will be seen
that there are three
kinds of appendages—l.
Ordinary stiff, cylindrical,
tapering, pointed hairs,
which are not connected
withany nerve. 2. Pale,
cylindrical hairs, with a
blunt termination and a
tuft of fine sete. These
hairs are connected witha
nerve,and Leydig regards
| them as organs of touch.
re 8. Peculiar cylinders, of

Fig. 35.—Terminal segments of one of the

smaller antennz of the water-woodlouse hy -
(Asellus aquaticus), x 500 (after Leydig). which there is one to each

a, Ordinary hairs (not connected witha geoment. They are come
nerve); 0, sensitive hairs (with a nerve at =.
the base); c, special cylinders (olfactory posed ot three parts
cylinders). 3 :
the middle one somewhat
wider than the others. The lower third is strongly chiti-
nized, like the ordinary hairs; the other two are more
delicate. At the free end he observed, in some cases,

a group of very fine, short hairs. At the base of

* Ann: and Mag. of Natural History, 1853.
+ “Ueber Geruchs und Gehérorgane der Krebse und Insekten,”
Miiller’s Ar., 1860. |

ORGANS OF SMELL IN CRUSTACEA—CENTIPEDES. 49

each cylinder is a nerve, which apparently swells into
a ganglion. |

Leydig described similar organs on the antenne
and palpi of various other Crustacea. They have
obviously some special function, and he suggests
that they are olfactory organs. It is interest-
ing that, in certain species which live in subter-
ranean waters and have lost their eyes, these olfactory
cones are unusually developed. They are much larger,
for instance, in Asellus cavaticus and Gammarus

See

Fig. 36.—Tip of the antenna of acentipede (Julus terrestris), x 600 (after Leydig).
At the apex are four olfactory cylinders, a few of which are also seen on the fol-
lowing segment, among the ordinary hairs.

puteanus, which live in the dark and are blind, than
in Asellus aquaticus and Gammarus pulex or G. fluviatilis.

Fig. 36 represents the end of the antenna of a centi-
pede (Julus terrestris), There are four olfactory
eylinders at the tip, and several are also seen on the
following segment among the ordinary hairs. In this
species the cuticle of the cylinder appeared sometimes
as if wrinkled, and Leydig believes that the end is
open.* Similar cylinders occur in Scolopendra, Glo-

* Loe. cit., p. 286.

50 OLFACTORY CONES IN INSECTS.

meris, and other centipedes. He also described similar
cones in certain insects. |

Further details with reference to the structure and
arrangement of these bodies have been given by Claus,
Sars, Weissman, Rougemont, Gamroth, Heller, Hensen,
Hauser, and others, who have also ascribed to them
this function. In Claus’s opinion, the nerve itself
enters these bodies. On this point, however, there is

Fig. 37.—End ofa palpus of Staphy-
linus erythropterus, x 600 (after
Leydig). a, Olfactory pit.

Fig. 38.—Part of antenna of Callianassa sub-
terranea. 6, Olfactory hairs; g, peculiar
curved hairs.

still much difference of opinion. At any rate, it seems
to be established, by the most recent observations, that
even if the cones are in some cases closed at the end,
they certainly remain open in others. Similar organs
also occur in the palpi (see Fig. 37).

Kraepelin describes other peculiar forms of hairs to
which he ascribes the perception of smell, as occurring
in all the stalk-eyed Crustacea (Podophthalmata).

~~

OLFACTORY HAIRS. a7

These olfactory hairs are partly round (Pontonia),
partly flat (Pagurus); the end is described as being
sometimes simply open (I'ig.39,a,b), sometimes provided
with a small cone (Fig. 39, ¢, d, e). The number of these
hairs is often very considerable. Moreover, they them-
selves sometimes bear, near the base, a number of very
fine bristles (Pagurus). There can, I think, be no doubt
that these hairs are organs of sense, and it is probable
that they are olfactory. The antenna of Callianassa
(Fig. 38) also bears another remarkable series of long,

e

Fig. 39.—Terminations of olfactory hairs of Crustacea. a, Of larva of a Paleemon3
b, of a Pagurus; c, of a Pinnotheres; @, of a Squilla ; e, of a Pontonia.

thin, movable, but stiff and hooked hairs (Fig. 38, g),
which also stand in direct connection with the nerve,
and have probably some sense-function.

In many eases the sense of smell is connected with
minute depressions in the integument. In spiders
Dahl has described a structure in the maxilla which he
believes to be olfactory. The skin presents a number
of minute orifices, under which he elongated cells, each
terminating in a nervous fibril.*

Leydig also mentions { the existence of small pits on

* “Das Gehor-und Geruchsorgan der Spinnen,” Arch. fiir Mie.
Anat., 1885.

+ “Ueber Geruchs und Gehororgane der Krebse und Insekten,”
Miiller’s Arch., 1860.

o2 OLFACTORY PITS.

the antenne and mandibular palpi of the crayfish
(Astacus fluviatilis) but 1 do not find any further
description of them. On the other hand, in insects they
play a more important part, and it will be convenient
to describe here very briefly the various structures
occurring on and in the antenne of insects, although it
is not to be supposed that they all serve for the sense
of smell. Newport* alludes to the “ pits”; but they
were first described by Erichson t; while Burmeister {
suggested that there are two classes—those containing
a hair, and those in which there is none. The pits are
only found in certain regions, and have certainly some
specific function. In the stag-beetle (Lucanus cervus)
the terminal plate of the antenna shows two large pits,
one on each side, and nearly opposite one another. In
other Lamellicorn beetles, as, for instance, in the cock-
chafer (Melolontha vulgaris), they are very numerous.
Lespes§ supposed them to be closed sacs, each containing
an otolithe. They certainly do present this appearance,
but the existence of any otolithe has been conclusively
disproved by Claparede,|]| Claus, Hicks, and others.
Graber thought J that he had discovered an organ
of hearing containing an otolithe in the antenne of
certain Diptera. Mayer,** however, has since examined
* Transuctions of the Entomological Society of London, vol. ii.

+ “De Fabrica et usu antennarum in Insectis.” 1847.

t “Deob. tiber den feineren Bau der Fiihlerfachur der Lamelli-
cornier.” 1848.

§ “Mem. sur l'appareil auditif des Insectes,” Ann. Sct. Nat , 1858.

| ‘Sur les prétendus organes auditifs des Antennes chez les
Coléopteres,”’ Ann. Sci. Nat., 1858.

q ‘‘Ueber neue otocystenartige Sinuesorgane der Insekten,” Arch.
fir Mic. Anat., 1879.

+* “Sopra ee organi di Senso nelle Antenne dei Ditteri,” tical
Acc. dei Lincet, 1878-79.

OLFACTORY ORGANS OF FLY. 53

them, and it appears to be really a sac lined with sense-
hairs.
Hicks * described the structure of tne antenne ina

O75 °409 090 002565
BO 9,200,803 20° 2 Son
sh23OsdG eae
B2905Gn 9 eo? ° 9 0
o9o000 200A
ce

og 0,

c

Fig. 40.—Antenna of blowfly (after Hicks). a, Enlarged third segment, showing
pits; c, base of the antenna.

considerable number of insects. On the antenna of the
blowfly (Musca; Fig. 40) he found no less than 17,000
perforations, each leading into a small sac, besides which

* Transactions of the Linnean Society, 1857-1859.

54 ANTENNA OF ICHNEUMON.

there are larger orifices leading into more complex de-
pressions, apparently arising from the confluence of a
number of thesimple sacs. At the base of these large sacs
are a number of papille, or small hairs. In the dragon-
fly, each segment of the antenna contains a large con-
voluted sac. The sacs, in fact, vary much in number,
size, and form, but Hicks considered that “they all
possess the same elements, and are formed on the same
principle.” In many cases he traced a nerve to the
base of the pits. He considered
that they were generally, if not
always, closed in by a deli-
cate membrane, which, indeed,
sometimes projected in a
hemispherical, conical, or even
hair-like form.

The minute structure of the
pits was further studied by
Leydig in 1860. He describes
Fig. 41.—One segment of the an- them as parts of the integument

Hickam Tehneumon (after “in awhich the chifine ageecs

thin, and more or less depressed,

with a hair in the centre. This hair may be even
reduced to a mere ring.

Hicks also called attention to a remarkable speciality
in the antenne of the Ichneumons, the true nature of
which he did not, however, correctly ascertain. He
describes the appearance presented as that of a great
number of narrow inverted canoes, with a keei-like
ridge, and each inverted over an oval perforation. He
regarded these as consisting of a thin transparent
membrane. Subsequent observations, however, have
shown that each supposed canoe-shaped membrane is,

OLFACTORY ORGANS OF WASP. 5d

in fact, a fine hair, inverted over one of the usual
pits.

In 1880 Hauser published an excellent memoir *
on the olfactory organs of insects, from which I have
taken Fig. 42, representing a section through part

Fig. 42.—Section througn part of the antenna of a wasp (after Hauser), x 430.
CH, Chitinous skin; Z, olfactory cone; G, olfactory pit; 7A, tactile hairs; HZ,
hypodermic cells; ¥/, the membrane surrounding them; K, nuclei of the olfac-
tory cells; K, remains of the earlier upper nucleus; SK, lower circle of rods;

RS, olfactory rod; GZ, Geisselzelle ; MZ, membrane forming cell; WM, membrane
closing the pit.

of the antenna of a wasp, showing two of the
olfactory cones, one projecting beyond the general
surface. ‘They terminate above in a fine rod, below in
a nerve-thread, and present a double series of ridges.

* “Phys. und Hist. Unt. ti. die Geruchsorgane der Insekten,” Zezt.
fiir Wiss. Zoot., 1880.

56 ANTENNAL ORGANS OF INSECTS.

Kraepelin* and Sazepinf have also published valuable
memoirs containing many interesting details.

The hairs of the antennee, then, serve some for touch
and some for smell, while there is, as we shall presently
see, strong reason for supposing that the sense of
hearing is also in some insects seated in the antenne.

The greatest variety of antennal organs, so far as we
yet know, occurs in the Hymenoptera (ants, bees, and
wasps). Of these I give a diagrammatic figure.
There are at least nine different structures.

1. Ordinary hairs (Fig. 43, ¢). .

Fig. 43.—Diagram showing structures on the terminal segments of the antenna of
insects. a, Chitinous cuticle; 0, Itypodermic layer; c, ordinary hair; d, tactile
hair; e, cone; f, depressed hair, lying over g, cup, with rudimentary hair at the
base ; hk, simple cup ; 7, champagne-cork-like organ of Forel; #, flask-like organ ;
l, papilla, with a rudimentary hair at the apex.

2. Hairs of touch (Fig. 43, d).

* « Phys. und Hist. Unt. ii. die Geruchsorgane der Insekten,” Zeit.
fiir Wiss. Zool., 1880; and “ Ueber die Geruchsorgane der Glieder-
thiere,” 1883.

+ “ Ueber den histol. Bau und die Vert. der nervésen Endorgane
auf den Fiihlern der Myriopoden,” Mém. de l Acad. Impér, de Sc. de
St. Petersburg, 1885.

ANTENNAL ORGANS OF INSECTS. 57

3. Flattened hairs (Fig. 43, ¢).

4. Depressed hairs (Fig. 43, /).

5. Pits with a minute hair at the base (Fig. 48, 9).

6. Pits without a hair at the base (Fig. 43, h).

7. Cones containing a nerve (Fig. 43, 2).

8. The champagne-cork-like organs of Forel (Fig.
43,72). These consist of a pit, with a constriction about
halfway up. They differ, in fact, from the second
sort mainly in the presence of this constriction.

9. The curious flasks (Fig. 43, &) first observed
and described by Hicks.* “They consist,” he says, “of

_asmall pit leading to a long delicate tube, which,
bending towards the base, dilates into an elongated
sac having its end inverted.” t Of these remarkable
organs there are about twelve in the terminal segment,
and one or rarely two in the others. Similar structures
have since been found in other Hymenoptera; but not,
I believe, as yet in any other order of insects. I have
ventured to suggest that they may serve as microscopic
stethoscopes. Kraepelin was disposed to regard them
as glands, but I agree with Forei that there is no suffi-
cient reason for doing so.

There may, moreover, be a distinctly characterized
sense-organ without any alteration of the actual
surface, as shown in some of the figures given by
Kraepelin, and also by that from Hauser given above
(Fig. 42).

These are, perhaps, the principal types, but there

* Transactions of the Linnean Society, vol. xxii. p. 39. Kraepelin
attributes the observation to Forel, but this is an error. Forel had
overlooked Hicks’s description and figure.

+ Hicks, “On the Organs of the Antennze of Insects,” Transactions
of the Linnean Society, vol. xxii.

08 COMPLEX STRUCTURE OF THE ANTENNZ.

are many modifications; for instance, complex pits
often arise from the confluence of several small ones.
The structure of the antenne is then very complex, and
increases with the importance of the antenne in the
lite of the insect. Among the Hymenoptera, Lyda has
about 600 pits; Tenthredo, 1200; Sirex, 2000; Pompilus,
3000; Paniscus, 4000; Ichneumon, 5000; Hylceus,
6000; the wasp (Vespa), about 13,000 pits and 700
cones; the blowfly, 17,000; the hive bee, according to
Hicks, about 20,000 pits and 200 cones. Among beetles
(Coleoptera) the numbers are generally small, but the
cockchafer (Melolontha) possesses, according to Hauser,
on each antenna as many as 35,000 in the female, and
39,000 in the male. Moreover, it is significant that in
those species where the females are quiescent and are
actively sought out by the males, the antenne are
much less highly developed in the female sex than in
the male.

As already mentioned, the antenne probably serve
partly as organs of touch, and in some cases for smell.

On the other hand, I do not believe that touch and
smell are the only two senses possessed by the antenne.
Forel and I have shown that in the bee the sense of
smell is by no means very highly devel: ped. Yet
their antenna is one of those most highly organized.
It possesses, as I have just mentioned, besides 200
cones, which may probably serve for smell, as many as
20,000 - pits; and it would certainly seem unlikely
that an organization so exceptionally rich should solely
serve for a sense so slightly developed.

Much as these antennal structures differ from one
another in form, arrangement, and structure, they are
all reducible to one type—to a hair—more or less de-

VARIOUS USES OF ANTENN/. Og

veloped, more or less deeply seated, standing in con-
nection with the ganglionic cells, and so with the cerebral
ganglia. Even the long-necked “bottles” (Fig. 43, £)
may be regarded as an extreme form of this type,
especially if the inversion at the end can be, as seems
probable, regarded as a hair.

All entomologists are agreed that some of the anten-
nal hairs serve as organs of protection, and others as
organs of touch. The evidence is, as we have seen, very
strong, that some of them serve as organs of smell.
They fulfil, therefore, at least three different functions,
and when we consider their manifold variety, there is
not only no @ przort improbability, but, on the contrary
it seems very probable that some of them, at least,
perform some other function in the animal economy.

There is, indeed, strong reason, as we shall see in the
next chapter, to believe that, in some cases at any rate,
the antennze act also as ears; while some of these
peculiar antennal organs, though obviously organs of
sense, seem to have no special adaptation to any sense
of which we are cognisant.

CHAPTER IY.
THE SENSE OF HEARING.

THE sensation of sound is due to vibrations of the air
striking on the drum of our ear. The intensity of the
sound depends on the extent or amplitude of the sound-
wave; while the pitch of the tone depends on the fre-
quence of vibration, and consequently on the number of
waves which strike the ear during a given interval.
The fewer the number of vibrations in a second, the
deeper the souud; the more numerous, the shriller it
becomes. Our pianos generally begin with the C of
32 vibrations in a second, and extend to A” of 3520
vibrations. The number of vibrations for the tone
A’, which is that of the hum of a bee, is about 440
in a second. If the vibrations are fewer than 30 in a
second, they produce only a buzzing and groaning
sound, while the shrillest sound we can hear is produced
by about 55,000 vibrations in a second.

It may seem curious that there should be any dif-
ficulty in ascertaining whether an animal can hear.
But, in the first place, in order to experiment on
them, we are often obliged to place them in situa-
tions very unlike those to which they are accustomed ;
and, secondly, it is by no means always easy to say

ORGANS OF SOUND—-MOLLUSCA—CRUSTACEA. 61

whether they are affected by a real noise, or whether
they are merely conscious of a concussion or vibration.

As regards the lower animals, it appears to me, I con-
fess, that many organs have been described as auditory,
on grounds which are anything but satisfactory. At
the same time, it cannot be doubted that many of the
lower animals do possess the power of hearing, especially
as some have elaborate organs for the production of
sound.

Among the lowest groups, none of the Protozoa or
Coelenterata are known to produce sounds, and in the
Mollusca, also, the power is very rare. The Pectens,
which are the most lively of bivalves, moving actively
by the sudden opening and closing of their valves—as
Pliny says, “Saliunt Pectines et extra volitant seque
ipsi carinant ”—also produce in the same way a certain
sound, which Aristotle * gives as an exceptional case
among the Mollusca.

Nor is the production of sound ‘itch more frequent
among the Crustacea. In one genus of crabs (Ocypoda),
the claw bears a rasp, or file, which can be rubbed against
a ridge on the basal segment of the limb, and thus
produces a harsh, jarring sound. Some of the lobsters
also (Palinurus) make a noise by rubbing one segment
of the antenne against another; but, considering that
the ear is well developed in this group, it is rather
remarkable how few of them are —— to possess the
power of producing sounds.

Passing on to the insects, the song of the Cicada has
been celebrated from time immemorial ; the chirping of
the crickets and grasshoppers is also familiar to us all.

For the reasons, however, already alluded to in the

#* * Historia Animalium.”

62 INSECTS—LOCUSTS.

preceding chapter, no insect possesses a true voice. The
sounds they make are produced in various ways-—for
instance, by the wings or the spiracles, by rubbing one
part of the body against another, etc.

The power of producing sounds audible to us is pos-
sessed by many insects scattered sporadically through
all the great groups.

In many of these cases, the power of producing sound
is confined to the males. ‘Their sounds are really love-
songs.” :

In Locusts, as Westwood says,t “The stridulating
powers of these insects must have attracted the notice
of every one who has walked through the fields in the
autumn. Unlike the insects of the two preceding
families, it is owing to the motion
of the hind femora, either con-
jointly or alternately rubbed
against the sides of the wing-
covers, that the sound is pro-
duced, the insects resting on their
four anterior legs during the
, operation ; the veins of the wing-
Fig. 44.—Leg of Stenobothrus covers being considerably ele-

pratorum (after Landois). :
vated, so-as to be easily acted
upon by the rugose inner edge of the thigh. Some
species, according to Goreau, may be observed to exe-
cute this movement without producing any sound per-
ceptible to our ears, but which he thinks may be per-
ceived by their companions.”

* The females are not, however, invariably dumb. In Ephippigera
both sexes are able to produce a sound, which, however, is not very
loud.

+ Westwood, ‘‘ Modern Classification of Insects.”

GRASSHOPPERS—CRICKETS. 63

Fig, 44 represents the leg of a grasshopper (Steno-
bothrus pratorum). On the inner side of the thigh, at
s, is a file, consisting of a row of fine teeth (Fig. 45, z),
which rub against the wing-covers, and thus produce the
well-known sounds.

Lehmann states that Brunelli “kept and fed several
males of Gryllus viridissimus in a closet, which were
very merry, and continued singing all the day; but a
rap at the door would stop them instantly. By practice
he learned to imitate their chirping ; when he did this
at the door, at first a few would answer him in a low
note, and then the whole party would take up the tune
and sing with all their might. He once shut upa male
of the species in his garden, and gave a female her
liberty ; but when she
heard the male chirp,
she flew to him im-
mediately.” *

In the males of
the house and field
crickets, the source of
the sound is different, Fig t6;5Sumtbow of stonsothrus, (ee
On the mner margin
of the left wing-cover, about one-third of its length
from the base, a thickened point is observed, from
which several strong veins'diverge. The strongest of
these veins, that running towards the base of the wing-
cover, 1s regularly notched on the under side trans-
versely, like a file. When the wing-covers are closed,
this oblique bar of the wing-cover lies upon the upper
suriace of the corresponding part of the right wing-

* “De Sensibus externis Animalium exsanguinium.” Gottingen:
1798. I give Kirby and Spence’s translation.

5

64 CICADAS—BEETLES.

cover, and when a tremulous motion is imparted to the
wing-covers, this bar rubs against the corresponding
bar of the right wing-cover, and thus produces the
familiar chirping sound.

The song of the Cicadas is produced, again, in a dif-
ferent manner. ‘The musical organs are internal, are
placed “at the base of the abdomen beneath, and are
covered by two large flat plates attached behind the
place of insertion of the hind legs, varying in form in
the different species, being, in fact, the dilated sides
of the metasternum. . . . [he sound issues out of two
holes beneath the above-mentioned plates, in a manner
somewhat analogous to the action of a violin.” *

Many beetles have special organs for the production of
sounds. A remarkable case is that of the so-called
“bombardier beetles,” which, when attacked, discharge
at the enemy, from the hinder part of their body, an
acrid fluid which, as soon as it comes in contact with
air, explodes with a sound resembling a miniature gun.
Westwood mentions, on the authority of Burchell, that
on one occasion, “ whilst resting for the night on the
banks of one of the large South American rivers, he
went out with a lantern to make an astronomical ob-
servation, accompanied by one of his black servant
boys; and as they were proceeding, their attention was
directed to numerous beetles running about upon the
shore, which, when captured, proved to be specimens
of a large species of Brachinus. On being seized, they
immediately began to play off their artillery, burning
and staining the flesh to such a degree that only a few
specimenscould becaptured with thenaked hand, leaving
a mark which remained a considerable time. Upon ob-

* Westwood, “* Modern Classification of Insects,” vol. il. p. 42. ~

THE BOMBARDIER BEETLE—PAUSSUS. 65

serving the whitish vapour with which the explosions
were accompanied, the negro exclaimed in his broken
English, with evident surprise, ‘Ah, massa, they make
smoke!’ ” *

A similar means of defence is possessed by beetles
belonging to a very different family—the Pausside.
Captain Boyes mentions t that on one occasion, having
captured a Paussus Fichteli “it immediately emitted
two loud and very distinct crepitations, accompanied
with a sensation of heat, and attended by a strong
acidulous scent. It left a dark-coloured stain on the
fingers resembling that produced by caustic, and
which had a strong odour something like nitric
acid. A circumstance so remarkable induced me to
determine its truth, for which purpose I kept it alive
till the next morning, and, in order to certify myself of
the fact, the following experiments were resorted to.
Having prepared some test-paper by colouring it with
a few petals of a deep red oleander, I gently turned
the Paussus over it, and immediately placed my finger
on the insect, at which time [I distinctly beard a crepi-
tation, which was repeated in a few seconds on the
pressure being renewed, and each discharge was ac-
companied by a vapour-like steam, which was emitted
to the distance of half an inch, and attended by a very
strong and penetrating odour of nitric acid.” ©

I do not, however, refer to these cases as affording
any evidence that the insects themselves possess the
power of hearing, but merely on account of their

* Westwood, “ Modern Classification of Insects,” vol. i. p. 76. °

Tt “The Economy of the Pausside,” Ann. and Magazine of Natural
History, vol. xviii.; see also Péringuay’s ‘“‘ Notes on Three Paussi,”
Transactions of the Eniomological Society, 1883, p. 133.

66 DEATH-WATCH—BURYING BEETLES.

intrinsic interest. The following instances, however,
do seem to imply a power of hearing.

A well-known case is that of the death-watch,
associated with so many superstitions, and supposed
in old days to be a certain indication of approaching
death. In this case the insect produces the sound by
tapping with its head or abdomen, or, according to
Doubleday, with its thorax. If a male death-watch
ticks, and there be a female even within several yards,
she returns the tap, and they approach one another
slowly, tapping at intervals, until they meet. The
male Ateuches stridulates to encourage the female in
her work, and also, according to Darwin, “from distress
when she is removed.” *

It has long been known that among the Longicorn
beetles many of the species, when alarmed, “ produce
a slight but acute sound by the friction of the narrowed
anterior part of the mesothorax, or rather a polished
part of the scutellum, against the edge of the protho-
racic cavity, by which motion the head is alternately
elevated and depressed. It has been generally stated
that it was by the friction of the hind margin of the
thorax against the base of the elytra that this sound
was produced, but this is not the case.”f The burying
beetles (Necrophorus) produce a sound by rubbing the
abdomen against the hinder edges of the wing-cases.

Wollaston, in a short paper on certain musical
Curculionide,} describes a species of Acalles, which he
found in Teneriffe. A number of specimens were in a
hollow stem, and when it was shaken “the whole plant

* ‘Descent of Man,” vol. i.
+ Westwood, “ Modern Classification of Insects,” vol. 1.
~ Ann. and Magazine of Natural History, 1860.

WEEVILS—COCKCHAFERS. 67

appeared musical.” In this genus the sound is produced
by rubbing the tip of the abdomen, so rapidly that the
movements were scarcely visible to the eye, against the
under surface of the ends of the elytra, or wing-cases,
The tip of the abdomen, though roughened, is not con-
spicuously so, the ends of the elytra are shagreened,
though very finely, and Wollaston expresses his surprise
that so small an instrument could produce so loud a
noise. He describes a similar structure in other species
of the group.

The cockchafers (Melolontha), besides the humming
of the wings, produce a sound which may almost be
called a voice. In the large trachea, immediately
behind each spiracle, is a chitinous process, or tongue,
which is thrown into vibration by the air during respi-
ration, and thus produces a humming noise.

In the beetles, then, the sounds produced may be
divided into three classes :

1. Incidental, such as those produced during
flight.

2. Defensive.

3. For signals, as in Longicorn beetles, Ateuches,
Anobium, ete.

Laudois gives the following summary of the different
modes in which sounds are produced by the Cole-
optera :—

1. Tapping sounds (Bostrychide, Anobium).

2. Grating sounds (Hlaterida).

3. Friction without rasping organs (Euchirus lon-
gimanus).

4. Rasping sounds produced by friction, viz.—

(1) Pronotum on Mesonotum (Cerambycida, with
the exception of Spondylis and Prionus).

68 VARIETY OF ORGANS OF SOUND AMONG BEETLES.

(2) Prosternum on Mesosternum (Omaloplia
brunnea).

(8) Elytra with rasp at the end (Curculionida ;
Dytiscida, Pelobius).

(4) Coxee with rasp (Geotrupes, Ceratophyus).

(5) Cover-margin rasp rubbing against the thigh
(Chiasognathus Grantit).

(6) Pygidium with two rasps in the middle
(Crioceris, Lema, Copris, Oryctes, Necro-
phorus, Tenebrionida).

(7) Abdomen with a grating-ridge and four
grating-plates (Trox sabulosus). |

(8) Abdomen with two toothed ridges rubbing
on cover-margin rasp (Elaphrus, Blethisa,
Cychrus).

(9) Elytra rubbing with under-wing rasp (Pelobius
Herrmann).

(10) Wings rubbing against abdominal ringlets
(Melolontha fullo).

5. Exploding sounds from the tail (Brachinus).

6. Sounds produced by the spiracles (Melolontha).

Graber, moreover, has shown by a number of
interesting experiments * that the power of hearing is
by no means confined to those beetles which are known
to produce sounds themselves.

Passing on to other groups of insects, flies and Finis
besides the humming of the wings, produce sounds,
like the cockchafer, through the spiracles, some of
which are especially arranged for this purpose. If a
fly be caught and held between the fingers, it will
generally make a loud and peculiar sound. The hum
of the mosquito is only too familiar to most of us.

* ‘Die Chordotonal Sinnesorgane der Insekten,” Arch. fiir Mie.
Anat., 1882.

DIPTERA—HYMENOPTERA. 69

-Landois. mentions that he has heard species of
Eristalis and Syrphus sing while they have been
sitting quietly. The dragon-flies (Libellulina) also
produce a sound by means of their spiracles,

Among Hymenoptera, the hum of an angry bee is
proverbial. Nor must I omit to mention the piping
noise made by young queen bees. It is well known
that there is only one queen in a hive, and that
working bees never turn their back on her; as she
moves among the combs, they all turn towards her.

If there has been a swarm led by the old queen, the
“young queen who has succeeded often makes a piping
noise, first noticed by Huber, whose statements are
generally recognized as correct.* While “singing”
the queen assumes a particular attitude, and the other
bees all lower their heads and remain motionless until
she begins to move again. In the mean while, if there
are any other young queens which have not yet left
the cells, they answer the old one, and their notes seem
to be sounds of challenge and defiance.

Other bees also produce a sound by means of their
spiracles quite different from the humming of their
wings. Mutdla Huropexa, a wingless species, related to
and not unlike the ants, makes, when alarmed, a rather
sharp noise by rubbing one of the abdominal rings
against the other.

Under these circumstances, Landois asked himself
whether other genera allied to Mutilla might not
possess a similar organ, and also have the power of
producing sound. He first examined the genus Ponera,
which, in the structure of its abdomen, nearly resembles

* Huber, “Obs. sur les Abeilles;” Bevan, ‘“‘ On the Honey a -
Langstroth, “On the Honey Bee.”

70 ANTS—BEES. —

Mutilla, and here also he found a fully developed
stridulating apparatus.

He then turned to the true ants, and here also he
found a similar rasp-like organ in the same situation. It
is indeed true that ants produce no sounds which are
audible by us; still, when we find that certain allied
insects do produce sounds appreciable to us by rubbing
the abdominal segments one over the other, and when
we find, in smaller species, an entirely similar structure,
it certainly seems reasonable to conclude that these
latter also do produce sounds, even though we cannot
hear them. lLandois describes the structure in the
workers of Lasius fuliginosus as having twenty ribs in
a breadth of °13 of a millimeter. In Lasius flavus I
found about ten well-marked ribs, occupying a Jength
of ;t, of an inch. Similar ridges also occur between
the following segments.

In the flies (Diptera) and dragon-flies (Libellulina),
the four thoracic spiracles produce sounds; while in-
Hymenoptera, as, for instance, in the humble bee
(Bombus), the abdominal spiracles are also musical.
The sounds produced by the wings are constant in
each species, excepting where there are (as in Bombus)
individuals of very different sizes. In these the
larger specimens give generally a higher note. Thus
the comparatively small male of Bombus terrestris
hums on A’, while the large female hums a whole
octave higher. There are, however, small species
which give a deeper note than larger ones, on account
of the wing-vibrations not being of the same number
in a given time. Moreover, a tired insect produces a
somewhat different note from one that is fresh, on
account of the vibrations being slower.

SOUNDS PRODUCED IN FLIGHT. val

Indeed, from the note produced we can calculate the
rapidity of the vibration. The slow flapping of a
butterfly’s wing produces nosound, but when the move-
ments are rapid a noise is produced, which increases
in shrillness with the number of vibrations. Thus the
house-fly, which produces the sound of F’, vibrates its
wings 21,120 times in a minute, or 330 times in a
second; and the bee, which makes a sound of A’, as
many as 26,400 times, or 440 times in a second. On
the contrary, a tired bee hums on LW’, and therefore,
according to theory, vibrates its wings only 330 times
~in a second. | ;

Marey has succeeded in confirming these numbers
graphically. He fixed a fly so that the tip of the
wing just touched a cylinder which was moved by
clockwork. Hach stroke of the wing caused a mark,
of course very slight, but still quite perceptible, and
he thus showed that there were actually 330 strokes in
a second, agreeing almost exactly with the number
inferred from the note produced.

The sound emitted from the spiracles ne no re-
lation to that produced by the wings. Thus, according
to Landois, the wing-tone of the hive ae is A’; its
“voice, if we may call it so, on the contrary, is an
octave higher, and often goes to B” and C”. In oneof
the solitary bees, Anthidiwm manicatum, the difference
is still greater; the wing-tone is G’, and the “voice”
- nearly two octaves higher, reaching to I”.

The wing-tone is constant, at least with the excep-
tions just alluded to. The “voice,” on the contrary,
appears to be to some extent under the control of the
will, and thus offers another point of similarity to a true
“voice.” ‘Thus a bee in the pursuit of honey hums

72 POWER OF VARYING SOUND.

continually and contentedly on A’, but if it is excited
or angry it produces a very different note. Thus,
then, the sounds of insects do not merely serve to bring
the sexes together; they are not merely “love-songs,”
but also probably serve, like any true language, to
express the feelings.

Landois also describes the muscles by means of
which the form of the organ, the tension of the drum,
etc., is altered, and the tone thus, no doubt voluntarily,
affected.* We can, indeed, onty in few cases distinguish
the differences thus produced; but as even we, far
removed as we are in organization, habits, and senti- —
ments, from a fly or a bee, can yet feel the difference
between a contented hum and an angry buzz, it is highly
improbable that their power of expressing their feelings
should stop there. One can scarcely doubt but that
they have thus the means of conveying other sentiments
and ideas to one another.

Butterfiies and moths do not habitually produce any
sound in flight. The texture of their wings is com-
paratively soft, and they are generally moved slowly.
Still, they are not altogether silent.

The death’s-head moth (Sphinz atropos) emits a
mournful ery, first noticed by Réaumur. This moth,
he says, “dans le temps qu'il marche, a un cri qui a
paru funébre; au moins est-il le cri d’une bonne ame
de papillon, s'il gémit des malheurs qu'il annonce.

“Te cri de notre papillon est assés fort et aigu; il a
quelque ressemblance avec celui des souris, mais il est
plus plaintif; ila quelque chose de plus lamentable.
C’est surtout lorsque le papillon marche, ou qu’il se

* «Die Ton and Stimm Apparate der Insekten,” Zeit. fiir Wiss.
Zool., 1866.

BUTTERFLIES—MOTHS. ts

trouve mal a son aise, qu’il crie ; il crie dans les poudries,
dans les boistes ot. on le tient renfermé; ses cris
redoublent lorsqu’on le prend, et il ne cesse de crier
tant qu’on le tient entre les doigts. En général il fait
grand usage de la faculté de crier, que la nature lui a
accordée.”’ *

There kas been much doubt how the sound arises, but
it appears to be ascertained that the moth produces it
by rubbing the palpi against the base of the proboscis.}

Huber thought, and subsequent writers—as, for
instance, Kirby and Spence, and Bevan—have con-
curred in the opinion, that the sound “operates on the
bees like the voice of their queen, and thus enables
the moth to commit the greatest ravages in the hives
with perfect immunity.” { On the cther hand, Huber
ascertained by experiment that it exercises no such
charm over humble bees. |

Several other species of the genus Sphinx also pro-
duce a sound, and a few other moths, for instance,
Noctua fovea. Darwin also mentions§ a Brazilian
butterfly, Ageronia feroma, as making “a noise like
that produced by a toothed wheel passing under a
spring catch, which could be heard at the distance
of several yards.”

The peacock butterfly (Vanessa 20) || is also said to
possess the same power.

For further details with reference to. the sounds
produced by insects, and, indeed, by animals generally,

* “ Mém. p. servir 2 ’ Histoire des Insectes.”

+ Landois, “ Die Ton und Stimm Apparate der Insekten,’’ Zett. fiir
Wiss. Zool., vol. xvii.

~ Bevan, “ On the Honey Bee.” § “Descent of Man,” vol. i.

|| “Die Ton and Stimm Apparate der Insekten,” Zezt. fiir Wiss.
Zool., 1867.

74 CENTIPEDES—SPIDERS.

I may refer to Landois’s interesting work, “Thier-
stimmen.”

From the fact that the power of producing sounds
audible to us is scattered among so many groups, and
that the sounds themselves are often so shrill, I am
disposed to suspect that many insects usually regarded
as dumb really produce sounds, which, however, are
beyond our range of hearing.

Among centipedes Gerstacker has described* a
sound-producing organ in Hucorybar crotylus. The
posterior legs have the fourth segment much enlarged
and leaf-like, with the edges raised and formed of
very hard chitine. The legs are rubbed against one
another, and thus produce a rasping sound. Bourne
also has recently described a stridulating organ in
another genus (Spherotherium). It is situated just
behind the twenty-first pair of legs, and consists of a
hood-like process bearing a number of parallel ridges.

There is a very general impression that spiders hear
well, and even enjoy music! There seems, however,
very little evidence of any value on the subject. No
doubt they are extremely sensitive to vibrations. The
presence of even a very small insect on their web is
at once perceived. Mr. Boys has shown that the
vibrations of a tuning-fork affect them strongly.
This sensitiveness to vibrations 1s, however, not neces-
sarily the same as a true sense of hearing. Kraepelin
says § that he knows only one observation which seems
to him to possess sufficient exactness to justify the
conclusion that spiders possess any sense of hearing—
namely, that of Lehmann. |

* Gerstacker, “‘ Stettin Ent. Zeit., 1854.
t Bourne, Linnean Journal, 1885. t Nature, vol. xxiii.
§ “Ueber die Geruchsorgane der Gliederthiere.”

POWER OF HEARING IN INSECTS. a

It would be, on the other hand, most unsafe to
conclude that spiders are incapable of hearing. Dahl*
has given reasons for believing that some of their hairs
serve as auditory organs. Westring has discovered,
in certain species of Theridium (T. serratipes, oculatum,
castaneum, etc.), a stridulating organ, consisting of a
sort of raised bow attached to the upper part of the
abdomen, which rubs against the under and hinder
part of the cephalothorax, producing a whirring sound.
Lebert f naturally observes that this appears to indicate
a power of hearing on their part.

As regards insects, it would be easy to multiply such
evidence almost indefinitely; I have given more illus-
trations than I should probably have otherwise thought
necessary, because so excellent an observer as Forel,
whose opinion I should value on such a point as much as
that of any authority, expresses doubt whether insects
really hear at all. “Ce qu’on semble,” he says, in his
last memoir on the subject, “ considérer comme preuve
de l’ouie me parait comme a Dugées reposer a peu d’excep-
tions pres sur des ébranlements mécaniques de lair ou
du sol qui sont simplement pergus comme tels par les
organes tactiles des insectes. Cela correspond a peu
pres a la derniére opinion de Graber sur” louie “de
la Periplaneta. Mais on n’a pas le droit de nommer
ouie de pareilles sensations.” t

Graber, however, has endeavoured to meet this
objection by an ingenious experiment.§ He placed
some water-boatmen (Corixa) in a deep jar full of

* “Das Gehor-und Geruchsorgane der Spinnen,” Arch. fiir Mie.
Anat., 1885.

+ “Die Spinnen der Schweiz.”

$ A. Forel, “Sensations des Insecies,” Recueil Zool. Suisse, t. iv. 1887.
§ Arch. fiir Mic. Anat., 1882.

76 SENSE OF HEARING IN INSECTS.

water, at the bottom of which was a layer of mud.
He dropped a stone on the mud, but the beetles,
which were reposing quietly on some weeds, took no
notice. He then put a piece of glass on the mud,
and dropped the stone on to it, thus making a noise,
though the disturbance of the water was the same.
The water-boatmen, however, then at once took flight.

In face of all the evidence, then, I do not think
there can reasonably be any doubt on the subject, and
it seems to be clearly established that insects do possess
the sense of hearing.

CHAPTER V.
THE ORGANS OF HEARING.

THAT many of the lower animals have special organs
for the production of sound, and possess the sense of
hearing, has been shown in the preceding chapter.

_ I now proceed to consider the mechanism by which
sounds are perceived. In our own ear we have; first
of all, the external ear, much less important in man
than in many other animals, as in the horse, for
instance, where it may be seen moving continually, and
almost automatically assuming the position most favour-
able for conveying the waves of sound down the outer
passage (Fig. 46, D) to the tympanum, ordrum. This is
a membrane stretched between the outer air on the one
hand, and the drum on the other, which also contains
air, transmitted through the mouth by means of the
Eustachian tube (Fig. 46, E). The drum is separated
from the brain by a hard, bony partition in which are
two orifices, one oval and the other round. Across the
drum stretches a chain of little bones (Fig. 47); first
the “hammer,” secondly the “anvil,” and lastly the
“stirrup.” ‘The fiat plate of the stirrup, again, lies
against the oval orifice, or fenestra ovalis, as it is techni-
eally called, of the drum. Thus the sounds are intensi-

78 STRUCTURE OF THE HUMAN EAR.

fied by being conveyed from the tympanic membrane
to one which is twenty times smaller. Behind the

Fig. 46.— Diagram of human ear (after Bernstein). D, Auditory canal; E, mouth of
Eustachian tube ; cc, tympanic membrane; B, tympanic cavity ; 0, fenestra ovalis ;
7, fenestra rotunda; s, semicircular canals; A, cochlea.

fenestra ovalis is the labyrinth, which is filled with fluid,

Am. Am, k

Fig. 47.—Ossicles of the ear. H, Hammer ;
Am, anvil; Am. k, shorter process of the
anvil; Am. 1, longer process of the anvil;
S, stirrup; S¢, long process of the
hammer.

and on which the final
filaments of the auditcry
nerve are distributed.
This fluid is thrown into
vibrations by those of the
stirrup, but as it is en-
closed in a bony case, the
vibrations would be greatly
curtailed if it were not for
the second membrane, or
fenestra rotunda. ‘This
round membrane, there-
fore, acts as a counter
opening, for if the fluid is

compressed in one place, it must claim more room in
another. The labyrinth consists mainly of two parts,

STRUCTURE OF THE HUMAN EAR. 79

the cochlea and the semicircular canals. The semi-
circular canals are three in number, and stand at right
angles to one another. No satisfactory explanation of
their function has yet been given; but there is some
evidence that, in addition to, or apart from, hearing,
they are affected by the position of the head, and thus
serve as organs for maintaining the equilibrium of the
body. Each of the canals commences with an oval
dilatation, or ampulla.
In the ampulla is a
projecting ridge, on
which are long, stiff,
delicate, hair-like pro-
cesses, the vibrations
of which probably give
certain sound-sensa-
tions. In the canals
certain parts bear
shorter hairs, over
which are minute ear-
stones, or otolithes,
consisting of carbonate
of lime, embedded in
agelatinous substance. _

Meeeeienled contains, ~ Gandcs ¥. Nowe, & trmeel alos h,
moreover, 2a compli- auditory hairs.

eated and wonderful organ, discovered by Count Corti.
This appears to be, in fact, a microscopic musical instru-
ment, composed of some four thousand complex arches,
increasing regularly in length and diminishing in
height from the base to the summit of the cochlea.
The waves of sound have been supposed to play on
this organ, almost like the fingers of a performer on
the keys of a musical instrument.

80 THE ORGAN OF CORTI.

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Te
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Soy]

& (6) 2 a=
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Fig. 49.—Tympanal wall of the ductus cochlearis, from the dog. Surface view from
the side of the scala vestibuli, after the removal of Reissner’s membrane, 29°. I.
Zona denticulata Corti. II. Zona pectinata Todd-Bowman: 1, Habenula sulcata
Corti; 2, Habenula denticulata Corti; 3, Habenula perforata Kolliker. III. Organ
of Corti: a, portion of the lamina spiralis ossea (the epithelium is wanting); 6 and
c, periosteal blood-vessels ; d, line of attachment of Reissner’s membrane ; é and
é, epithelium of the crista spiralis ; f, auditory teeth, with the interdental furrows;
9 9, large-celled (swollen) epithelium of the sulcus spiralis internus, over a certain
extent shining through the auditory teeth ; from the left side of the preparation
they have been removed ; A, smaller epithelial cells near the inner slope of the
organ of Corti; k, openings through which the nerves pass; 7, inner hair cells;
l, inner pillars ; m, their heads; o, outer pillars; », their heads; p, lamina
reticularis ;_g, a few mutilated outer hair cells; 7, outer epithelium of the ductus
cochlearis (Claudius’s cells of the author’s); removed at s in order to show the
points of attachment of the outer hair cells. After Waldeyer, in Stricker’s
“ Manual of Histology.”

MODE OF ACTION OF AUDITORY ORGANS. 8]

The fibres of Corti, according to Helmholtz, may
be distributed among the seven octaves which are in
general use, so that there will be 334 fibres to every
semitone, and 400 to each octave. Weber has esti-
mated that a skilful ear can perceive a difference even
of the J; of a tone, or nearly four thousand sounds, and
this would agree fairly well with the number of fibres.

But why, it may be asked, should a given musical
sound act more on one of these “ keys” than another ?
If several tuning-forks which sound different notes
are placed on a table, and another in vibration be
brought near.them, the one sounding the same note is
thrown into vibration, while the others are unaffected.
A second tuning-fork would affect its own fellow, but
no other, and so on.* A very slight change in the
tuning-fork, such, for instance, as would be made by
fastening a piece of wax to one of the prongs, is
sufficient to destroy the sympathetic vibrations. The
sound of the human voice has been known to break a
bell-shaped glass by the agitation thus caused. The
difficulty is to hit the pitch with sufficient precision,
and retain the tone long enough. It is probable,
therefore, that each of Corti’s arches is set for a
particular sound, and sensitive to it alone. This
suggestion derives additional probability from the
observations of Hensen (see p. 93) on the auditory

hairs of Crustacea.

We thus obtain a glimpse, though but a glimpse, of
the manner in which the arches of Corti may possibly
act. There are many problems still to be solved, but
it is at least easy to see that so complex an organ may
be capable of conveying very complex sensations.

* Helmholtz, “ Sensations of Tone.”

82. ORGANS OF HEARING IN THE LOWER ANIMALS.

On THE ORGANS OF HEARING IN THE LOWER
ANIMALS.

The semicircular canals in the human ear (see p. 79)
have been supposed by some, in addition to, or apart
from, their functions as organs of hearing, to assist in
maintaining the equilibrium of the body; at all events,
when they are injured, the movements frequently be-
come disorderly, and the otolithic organs of the lower
animals appear, at any rate in certain cases, to perform
a similar function.*

Otolithes, as we have seen, are present In our own
ears, but they play a much more important part in
those of the lower animals. In the lowest, the sound-
waves may be considered to produce a certain effect
upon the general tissues. ‘The soft parts of the body
are, however, not well calculated to receive such
impressions. Their effect would be heightened by the
presence of any solid structures, whether spicules, as
in sponges, etc., or solid hairs projecting from the
general surface, as in a great many of the lower
animals.

The Meduse (jelly-fishes, Fig. 50) present round the
edge of the umbrella certain “marginal bodies,” with
reference to which there have been great differences of
opinion. O. F. Miller, by whom they were discovered,
regarded them as orifices for the exclusion of digested
food, Rosenthal and Escholtz considered them to be
glands, Milne Edwards as ovaries; but it seems now
clearly established that some are organs of hearing,

* Delage, “Sur une fonction nouvelle des Otocystes,” Arch. d. Zool.

Ezp., 1887. Engelmann, “ Ueber d. Function der Otolithen,” Zeol.
Anz., 1887.

MEDUSZ.

Fig, 50.—Zutima gigas (after Haeckel).

83

84 - MEDUSA.

and others of sight. Some species possess both, but, as
a general rule, among Meduse, where organs of hearing
are present, those of sight are wanting, and wee versa.
It may seem extraordinary that there should be such
differences of opinion as to these organs. The earlier
naturalists, however, had but imperfect microscopes,
and probably often examined specimens in a bad state
of preparation. As regards the alternative between
the view that they served as eyes and that which
regarded them as ears, it must, moreover, be remem-
bered that as long as we merely know that there was
a capsule containing a transparent body, the function
might well be doubtful.

The auditory organs of the jelly-fishes were first
recognized as such by Kolliker.* They are ranged
round the umbrella, and vary considerably in number,
ranging up to sixty in Cunina, eighty in Mitrocoma,
and as many as six hundred in Ciquorea. |

There are three types. In the first, the auditory
organ is an open pit, lined with cells. The majority of
those on the outer side contain an otolithe, while a row
on the opposite side are strap-
shaped, their free ends termi-
nating in auditory hairs, which
reach to the cells containing
the otolithes, while their inner
ends are continuous with fibres
from the inner nerve-ring. __
Fig. 51.— Auditory organ of Ontor- In such an auditory organ

“de cee as that of Ontorchis (Fig. 51),
the otolithes present a very deceptive resemblance to
the lenses of an eye.

* “Ueber die Randkorper der Quallen,” Irorieps Neue Not., 1843,

MEDUS&. 85

Fig. 52 represents the somewhat more complex
auditory organ of Phialidium.

Fig. 52.—Auditory organ of Phialidium (after Hertwig). d*, Epithelium of the upper
: surface of the velum; d’, epithelium of the under surface of the velum; Ah,
auditory hairs; h auditory cells; np, nervous cushion; m7’, nerve-ring; 7,
circular canal at the edge of the velum.
The second type is more advanced, the vesicle being
closed, and the otolithes fewer in number, the Eucopide,
indeed, having only one.* :

In the third type, that of the Trachymedusz, the

Fig. 53.— Auditory organ of Rhopalonema, still showing a small orifice (after Hertwig).
hk, Modified tentacle; 0, auditory organ.

auditory organs are modified tentacles. They form a
club-shaped body, with a central endodermal axis, and

* Hertwig considers that the supposed hairs shown by Hensen in
his figure of the ear of Eucope are really the edges of auditory canals.

86 MEDUS&.

bearing at the apex one or more sometimes spherical,
sometimes prismatic, otolithes. In some cases the
organ becomes enclosed in a cup, which in Gena
closes at the top.

In another family of the Hydromeduse, the Ocasmiies
these organs are absent, and appear to be replaced by
certain pigment spots at the base of the tentacles,
which, however, from their structure are considered to
be rudimentary organs of vision, and will be described
in the chapter on eyes.

Some species have, in addi-
tion, other organs, obviously of
sense, but the function of which
is still far from clear. Fig. 54
represents one of these curious
sense-organs in Pelagia, after
Hertwig. It is in the form of
a somewhat bent finger, is
situated in a deep fold of the
umbrella, contains a branch of
the gastrovascular canal, and is
filled at the tip with a group of
Fig. 54.—Sense-organ of Pelagia Solid, shining, rod-like crystals.

(after Hertwig). o, Group of : ; : E
crystals; sk, sense-organ; sf, The auditory organ in worms
fold of the skin; ga, gastro-vas. :

cular chanueh oe and —mollases “cousisks > aspieee

closed vesicle, containing one
or more otolithes, and lined with nerve-cells, which are,
in the higher groups, connected at their base with the
auditory nerve, and bear setee at the other end. De
Quatrefages was the first who established clearly the
existence of auditory organs in worms.
In the Mollusca, the existence of an organ of hearing
in some Gasteropods was justly inferred by Grant from

MOLLUSCA—ANNELIDES. 87

the fact that one species, Tritonza arborescens, emits
certain sounds, doubtless intended to be heard by its
fellows.

The cilize contained in the auditory vesicle are some-
times short, and scattered over
the general surface, as in Unio
(Fig. 55); sometimes long and
borne on papillary projections, as
in Carinaria and Pterotrachea *
(Fig. 56), where also there are
certain special cells, supposed to

-actas buffers or dampers. The
otolithe is sometimes single, and e Binio (after Leydig) Nees :
nearly spherical, asim Acephala "> “*} © owlne
and Heteropoda, and consists of calcareous matter with
an organic base; in the Gasteropods, Pteropods, and

Fig. 56.—Auditory organ of Pterotrachea Friderici (after Claus). Na, Auditory nerve;
¢, central cells; d, supporting plate; 6, outer circle of auditory cells; a, ciliated
cells.

some Annelides (Arenicola, Amphicora) they are
* Claus., “ Ueber den Acoust. App. im Gehororgane der Hetero-

poden,” Arch. fiir Mic. Anat., 1878.
6

88 ANNELIDES-——CRUSTACEA.

pumerous, and sometimes, as in Cymbulia, collected
into a mulberry-like group.

In many cases the auditory sac rests directly on the
ganglion. |

The actual mode of termination of the nerves js still
uncertain. I have already mentioned that vibrations, if
fewer than thirty in a second, do not produce on us the
effect of sound. But it is possible that these organs in

the lower animals are intended quite as much to record |

movements in the water as for hearing properly so called.

THe ORGANS OF HEARING IN CRUSTACBRA.

ee
rk
Ba

a

ey;
EY j
E 4? |

7 3s
>

Fig. 57.— Base of
right antennule of
lobster (Astacus
marinus), after
Farre. a, Orifice ;
S, Sac.

2
Fig. 58.—Interior of auditory sac of Ichster (after
Farre). a, Oritice; b, auditory hairs.

It was long supposed that the auditory organ of the ~

Crustacea was situated in the basal segment of the

outer antenna. The true auditory organ was, indeed,

discovered by Rosenthal in 1811,* who, however, re-
* Reil’s Arch. fiir Phys., 1811.

be é br -" A si ail _ . “ Pe gh ™ of’ = a. - -
ee ee ee ee ee ee a ee eee ee ee eae ee ee, ee ee ae La eT eT

CRUSTACEA. 89

garded it as an olfactory organ, as did also Treviranus,
Fabricius, Scarpa, Brandt, Milne Edwards, and, in fact,
the older naturalists generally. ‘’he discovery of its
true nature is due to Farre,* was confirmed by Huxley Tf
and Leuckart, and is now generally admitted. It is
a sac situated in the base, or first segment, of the
lesser pair of antennz, which is slightly dilated. In
some species the sac communicates freely with the

Fig. 59.—Part of wali of auditory sac of lobster (Astacus marinus); after Hensen.
a, Thickened bars in the membrane of the sac ; », first row of auditory hairs; n’,
second row of auditory hairs; n”’, third row of auditory hairs; »’/”, fourth row of
auditory hairs; ¢, grains of sand, serving as otolithes.

water by means of an orifice situated towards the inner

and anterior margin, and guarded by rows of fine

hairs. In others the orifice as closed,-but its position
is always marked, as the auditory sac is at this point
eonnected with the skin.

Both contain otolithes. Those of the closed sacs are
generally rounded; while, on the contrary, those of

* Philosophical Transactions, 1843.
7 Ann. and Mag. of Natural History, 1851.

90 USE OF GRAINS OF SAND AS OTOLITHES.

the open sacs are simply grains of sand, and are so
numerous as sometimes to occupy one-fourth, or even
one-third, of the sac.

Farre stated that the otolithes in the avai SACS
of Crustacea were simply grains of sand, selected by
the Crustacea, and put into their own sacs to serve as
otolithes. It seemed, however, so improbable that
Crustacea should pick up suitable particles of sand
and place them in their ears, that the statement was
not unnaturally received with incredulity. The obser-
vation of Hensen appears, however, to leave no doubt
on the subject. The sac, whether open or closed, is an
extension of the outer skin, and is cast with it at each
moult. Hensen examined them shortly after moulting,
and found that the sacs contained no stones; he saw
the shrimps carefully selecting particles of sand, but
could never detect one in the very act of placing
one in the auditory sac. He therefore placed some
shrimps in a vessel of filtered sea-water, and strewed
over the bottom some crystals of uric acid. Soon
afterwards one of the shrimps moulted, and the auditory
sac was found on examination to contain a few grains
of sand, but no erystals of uric acid. Three hours
later, however, Hensen found that the new sac con-
tained numerous erystals of uric acid, but none re-
sembling common sand. LHvidently, therefore, the
Crustacea pick up grains of sand, and actually intro-
duce them into their own ears to serve as otolithes.

Otolithes are not, however, universally present. In
the true crabs (Brachyura) they appear to be always
wanting, so that the auditory hairs (which present very
nearly the same character as those of the lobsters, etc.)
are capable of being thrown into vibrations without the
mediation of otolithes.

AUDITORY HAIRS. OQ]

The interior of the sac is thus described by Farre:
“ Along the lower surface of the vestibular sac is seen
running a semicircular line, broader at its upper than
its lower exiremity (Fig. 58, 6). ‘This part is more
easily examined after the sand has been washed away
by agitation under water. Itis then seen, with a power
of 18- linear, to consist of several rows of ciliated pro-
cesses, of which one row is more regular and prominent
than the rest, and crests the entire margin of the
ridge. The processes diminish in size and number
on either side, and are in some places seen in groups,
but always assume the general form represented in”
Fig. 58.

In Astacus there are four rows of hairs. The first
are somewhat scattered, and above the otolithes; the
second consists of larger bairs, arranged close together ;
the third and fourth are smaller again, and more scat-
tered. ‘These three rows of hairs are covered by the
otolithes. They stand in connection with the terminal
fibrils of the acoustic nerve, and through their vibra-
tions the sense of sound is supposed to be conveyed.
In the lobster Hensen counted 548 auditory hairs.
He divides auditory hairs of Crustacea into three
classes: otolithe hairs; free hairs, enclosed in the audi-
tory sac; and auditory hairs on the outer body surface.

These latter auditory hairs (Fig. 59) are situated
over an orifice in the chitinous integument, and stand
in direct communication with a fibril from the nerve;
the stem of the hair does not rest directly on the
chitinous integument, but is supported by a delicate
membrane, which is sometimes dilated at the base; the
edge of the chitine at one side of the hair is raised into
a tooth; lastly, according to Hensen, each auditory hair

92

EAR IN TAIL OF: MYSIS.

possesses a sort of appendage, or sesh to which the
nerve is attached.

ce

Fig. 60. — Auditory
hair of the crab
(Carcinus menus),
x 500. a, Skin; ¢,
nerve; A, delicate
intermediary mem-
brane or hinge (after
Hensen).

As far as details are concerned—the
form of the sac, the number, form, and
arrangement of the hairs, etc.—the
auditory organs of the Crustacea offer
endless variations in the different species,
while very constant in each.

In the higher groups the anditory
sac is always at the base of the small
antenne. In one of the lower forms,
however—the curious genus Mysis—_
the ear is situated in the tail.

The genus Mysis (Fig. 61) is a group
of Crustaceans, in outward appearance
very like shrimps, but differing in the
absence of external gills, and in the
structure of the legs and other par-

ticulars, so that it is placed ina different family. Frey
aud Pouce moreover, made the interesting he
that it possesses two ears in its tavl.

Fig. 61.—Mysis (after Frey and Leuckart).

The tail, like that of a lobster, consists of five flaps.
In each of the two smaller flaps is an oval sae (ig. 62)
containing a single, lens-shaped otolithe, consisting of

MODE OF HEARING. 93

a calcareous matter embedded in an organic substance.
That Crustacea do, as a matter of fact, possess the power
of perceiving sounds, there can be no doubt. Hensen
himself has made various experiments on the subject.
Moreover, strychnine possesses the peculiar property of
augmenting the reflex power of the nervous centres.
Taking advantage of this, Hensen placed some shrimps
in sea-water containing strychnine. He then found
that they became ex-
tremely sensitive to even
very slight noises. Further
than this, Hensen availed
himself of Helmholtz’s re-
searches on the perception
of sound, and, suspecting
that the different hairs
might be affected by ditf-<
erent notes, found that was
actually the case. |
Lhe vibration of the hairs
is mechanical, not depend-
Meeeon yihe life of the: Ms: 6%. Tall of Morte wdgarts, show.
animal. Hensen took a
Mysis, and fixed it in such a position that he could watch
particular hairs with a microscope. He then sounded
ascale; to most of the notes the hair remained entirely
passive, but 1o some one it responded so violently and
vibrated so rapidly as to become invisible. When the
note ceased, the hair became quiet; as soon as it was
resounded, the hair at once began to vibrate again.
Other hairs in the same way responded to other notes.
The relation of the hairs to particular notes is probably
determined by various conditions; for instance, by its
length, thickness, ete.

94 ORGANS OF HEARING IN INSECTS.

That these plumose hairs, then, really serve for hear-
ing may be inferred, not only from their structure and
position, but also from the observed fact that they
respond to sound-vibrations.

Hensen’s observations* have been repeated and
verified by Helmholtz.

THE ORGANS OF HEARING IN INSECTS.

IT now pass on to insects. There has been great
difference of opinion as to the seat of the organ of
hearing in this group.

The antennz have, as already mentioned, been re-
garded as ears by many distinguished authorities,
including Sulzer, Scarpa, Schneider, Bolk-Hausen,
Bonsdorff, Carus, Strauss-Diirkheim, Oken, Burmeister,
Kirby and Spence, Newport, Landois, Hicks, Wolff
and Graber, who have supported their opinion by
numerous observations.

Kirby states that once “a little moth was reposing
upon my window; I made a quiet, not loud, but distinct
noise: the antenne nearest to me immediately moved
towards me. I repeated the noise at least a dozen times,
and it was followed every time by the same motion of
that organ, till at length the insect, being alarmed,
became more agitated and violent in its motions.”
And again: “I was once observing the motions of an
Apion (a small weevil) under a pocket microscope ; on
seeing me it receded. Upon my making a slight
but distinct noise, its antenne started. IJ repeated tle
noise several times, and invariably with the same
effect.” T

* ¢ Sensations of Tone.”
+ Introduction to “ Entomology,” Kirby and Spence, vol. iv.

BEETLES. 95

Among beetles, the genus Copris, “particularly,” says
Newport, “ Copris molossus, in which I first remarked
it, have the antenne composed of ten joints, the last
three of which form the knob or club with which it is
surmounted.

“When the insect is in motion, these plates or audi-
tory organs, if we may be allowed so to call them, are
extended as wide as possible, as if to direct the insect
in its course; but upon the occurrence of any loud but
sudden noise are instantiy closed, and the antenne
retracted as if injured by the percussion, while the
insect itself stops and assumes the appearance of death.
A similar use of the antennze is made by another family,
Geotrupidee, which also act in the same manner under
like circumstances.

“These facts, connected with the previous experi-
ments, have convinced me,” he says, “that the antennze
in all insects are the auditory organs, whatever may
be their particular structure; and that, however this
is varied, it is appropriated to the perception and
transmission of sound.” f

Will has made some interesting observations on
some of the Longicorn beetles (Cerambyx), which
tend to confirm this view. These insects produce
a low shrill sound by rubbing together the prothorax
and the mesothorax. The posterior edge of the
prothorax bears a toothed ridge, and the anterior end
of the mesothorax a roughened surface, and when these
are rubbed together, a sound is produced something
hke that made by rubbing a quill on a fine file.

* Newport, “On the Antenne of Insects,’ Transactions of the
Entomological Society, 1856-40, vol. ii.

96 BEETLES.

Will took a pair of Cerambyx (beetles), put the
female in a box, and the male on a table at a distance
of about fifteen centimetres (four inches). They were at
first a little restless, but are naturally calm insects, and
soon became quiet, resting as usual with the antennee
half extended. The male evidently was not conscious
of the presence of the female. Will then touched the
female with a long needle, and she began to stridulate.
At the first sound the male became restless, extended
his antenne, moving them round and round as if to
determine from which direction the sound came, and
then marched straight towards the female. Will
repeated this experiment many times, and with dif-
ferent individuals, but always with the same result. As
the male took no notice of the female until she began
to stridulate, it is evident that he was not guided by
smell. From the manner in which the Cerambyx was
obviously made aware of the presence of the female by
the sound, Will considered it clearly proved that in
this case he was guided by the sense of hearing.

Will has also repeated with these insects the experi-
ments I made with ants, bees, and wasps, and found
that they took no notice whatever of ordinary noises ;
but when he imitated their own sounds with a quill
and a fine file, their attention was excited—they
extended their antenne as before, but evidently per-
ceived the difference, for they appeared alarmed, and
endeavoured to escape.*

Hicks in 1859 justly observed that, “ Whoever has
observed a tranquilly proceeding Capricorn beetle which
is suddenly surprised by a loud sound, will have seen

* Will, “ Das Geschmacksorgan der Insekten,” Zeit. fiir. Wiss. Zool.,
1885,

SEAT OF THE SENSE OF HEARING. Q7

how immovably outward it spread its antenne, and
holds them porrect, as it were with great attention, as
Jong as it listens, and how carefully the insect proceeds
in its course when it conceives that no danger threatens
it from the unusual noise.” *

Other similar observations might be quoted, but
these sufficiently indicate that in some insects, at any
rate, the organs of hearing are situated in the antenne.

On the other hand, Lehmann long ago observed
that the house cricket (Acheta domestica), when
deprived of its antenne, remained as seusitive to
sounds as previously. This is. quite correct; and yet, if
a cricket be decapitated, and a shrill noise be made
near the head, the antenne are thrown into vibration
by each sound.

In fact, not only do the highest authorities differ,
but the observations themselves appear at first sight
to be contradictory. The explanation seems to be that
the sense of hearing is not confined to one spot. That
the antennz do serve as ears, at least in some insects,
the evidence leaves, I think, no room for dveubt. But
there is no reason, in the nature of things, why the
sense of hearing should be confined to one part of tie
body. ‘Taste, indeed, would be useless except in or
near the mouth, and almost the same may be said of
smell. But the sense of touch is spread, in greater or
less perfection, over the whole skin. Indeed, there is
among the lower animals a great tendency to repeti-
tion, and not least so amongst insects. The body con-
sists normally of a number of segments, each with a
pair of appendages and a ganglion. There are three
pairs of legs; two pairs of jaws, opening, not vertically,

* Transactions of the Linnean Society, vol. xxii.

98 DIFFERENT SEATS OF ORGANS OF SENSE.

as ours do, but laterally; several pairs of breathing-
holes arranged along the sides of the body; and two
kinds of eyes. Moreover, unquestionable organs of
sense occur in very different parts of the body. The
Crustacean genus Mysis, as already mentioned, has ears
in its tail; one group of sea-worms (the Polyoph-
thalmata) have a pair of eyes on each segment of the
body.

Of Amphicorine, a small worm of our coasts, M. de
Quatrefages says that often,* “C’est la queue qui marche
la premiere, explorant évidemment le terrain avec une
erande activité et donnant autant de signes d’intelli-
gence et de spontanéité que pourrait le faire la partie
antérieure du corps. ... Cette queue porte a son
extremité un disque élargi sur lequel sont placés deux
points rouges. . . . Je ne
mets nullement en doute que
ces points ne solent en effet
des organes de vision.” He
was not able, indeed, to make
out their finer structure. On
the other hand, the lateral
eyes of the Polyophthalmata
possess a well-formed lens.

We need not, then, assume
that the organs of hearing
in insects must necessarily
be in the head, or, indeed,
Fig. 63.—Part of leg of Grasshopper that they need be Senn

Sib iaer Graber. os to.% trated | 1 OG” pari ae me
body.

It had long been known that grasshoppers and

* Ann. des Sci. Nat., 1850.

CRICKETS HAVE EARS IN THEIR LEGS. 99

crickets have on their anterior legs two peculiar, glassy,
generally more or less oval, drumlike structures; but
these were supposed by the older entomologists to
serve as resonators, and to reinforce or intensify the
well-known chirping sounds which they produce.

. Johannes Miller was the first who suggested that
these drums, or tympana, act like the tympanum of our
own ears, and that they are really the external parts
of a true auditory apparatus. That any animal should
have its ears in its legs sounds, no doubt, a priore
very unlikely, and hence probably the true function of
this organ was so long unsuspected. That it is, how-
ever, a true ear the following particulars, taken
especially from the memoirs of Miiller,* Siebold,f
Leydig,t Hensen,§ Graber,|| and Schmidt,7 conclusively
prove,

The Leaping Orthoptera fall into three well-marked
groups: the locusts (Locustide), which have short
antennsz; the crickets (Achetide), which have long
antennee, and the wings flat on the back; and, thirdly,
the Gryllide, or grasshoppers (as I may perhaps call
them), which have also long antenne, but in which
the wings are sloping. This is the nomenclature
adopted by English authorities, such as Westwood ;
but unfortunately many foreign entomologists call the

* «Zur vergleichenden Physiologie des Gesichtsinnes.” 1826.

+ “Ueber die Stimm und Gebhdérorgane der Orthopteren,” Arch. fiir
Natur geschichte, 1844.

ft “Ueber Geruchs-und Gehororgane der Krebse und Insekten,”
Reicherts’ Arch. fiir Anat., 1860.

§ “Ueber das Gehororgan von Locusta,” Zeit. fiir Wiss. Zool., 1866.

| “‘ Die Tympanalen Sinnesapparate der Orthopteren,” Arch. ftir
Mic. Anat., vol. xx., 1875.

| “Die Gehororgane der Heuschrecken,” Arch. fiir Mic. Anat.,
vol. xi.

100 EAR OF GRASSHOPPERS. ;

crickets Gryllide, the grasshoppers Locustide, and the
locusts Acridiidee.*

In grasshoppers (Gryllide) and crickets (Achetidee)
the auditory organ lies in the tibia of the anterior leg,
on both sides of which there is a disc (Fig. 63), generally
more or less oval in form, and differing from the rest
of the surface in consisting of a thin, tense, shining
membrane, surrounded wholly or partially by a sort of
frame or ridge. In some species the two tympana are
similar in form; in others they differ. For instance, in
the field friclents the hinder tympanum is elliptic,
the front one nearly circular in outline.

In many of the Gryllide, the tympana are protected
by a fold of the skin, which projects more or less over
them. ‘The corresponding spiracle is also specially
modified in the stridulating locusts, while in those
which are dumb it is formed in the same manner as
the others.

The tympana are not always present, and it is an
additional reason for regarding them as auditory organs,
that both among the Achetide and the Gryllida, in
those species which possess no stridulating organs, the
tympana are also wanting.T

* The destructive “locust” of the East, which is so numerous that
in one year our Government! in Cyprus destroyed no less tlian
150,000,000,000 of eggs, and whose ravages are used in Eastern poetry
as types of destructiveness, has short antenne, and belongs to the first
division; to which, therefore, English entomologists apply the name
Locusta, while our foreign friends, on the contrary, apply the name to
a totally different insect. However, I merely refer to this now, to explain
why the terms I have used do not in all cases agree with those
adopted by the observers to whom I am referring.

+ This rule seems, however, not to be entirely without exceptions.
At least, Aspidonotus and Hetrodes are said to possess tympana, but

1 Report on the Locust Campaign, Parl. Paper, 5250 of 1888.

Bel
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BUS. ARS

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STRUCTURE OF BAR. 101

Graber regards the covered tympana as a develop-
ment from the open ones, and suggests that in time
to come the species in which the tympana are now
exposed may develop a covering fold.

If now we examine the interior of the leg, the trachea
or air-tube will be found to be ele oky modified.
Upon entering the tibia it immediately enlarges and
divides into two branches, which reunite lower down.
To supply air to this wide trachea the corresponding
spiracle, or breathing-hole, is considerably enlarged,
while in the dumb species it is only of the usual size.
An idea of the form of the trachea will be given by
Fig. 69, which, however, represents the anterior tibia
of an ant, where these trachez are less considerably
enlarged, and where one of the branches is much smaller

than the other, while in locusts they are nearly equal

in width, and one lies against each tympanum... The
enlarged trachea occupies a considerable part of the
tibia, and its wall is closely applied to the tympanum,
which thus has air on both sides of it; the open air on
the outer, the air of the trachea on its inner surface.
In fact, the trachea acts like the Eustachian tube in
our own ear; it maintains an equilibrium of pressure

no stridulating apparatus. for instance, in the following forms, both
the stridulating apparatus and the tympana are absent, viz. :—

Among the CGicanthide: Phalangopsis and GryHomorpha (both are
wingless).

Platydactylide: Metrypa and Parametrypa (both wing-
less).

Tettigonide: Trigonidium.

Gryllide: Gryllus apterus, Parabrachytrupes Australis,
and Apiotarsus (all wingless).

Gryllotalpide: Tridactylus apicalis.

Mogoplistide: Mogoplistes, Myrmecophila, Physoblemma
(all wingless), and Cacoplistes.

102 STRUCTURE OF EAR.

on each side of the tympanum, and enables it freely

to transmit the atmospheric vibrations.

These trachee, though formed on a similar plan,
present many variations, corresponding to those of
the tympana, and showing that the tympana and
the trachee stand in intimate connection with one
another. For instance, in those species where the
tvympana are equal, the trachee are so likewise; in
Gryllotalpa, where the front tympanum only is de-
veloped, though both tracheal branches are present, the
front one is much larger than the other; and where
there is no tympanum, the trachea remains compara-
tively small, and even in some cases, according to
Graber, undivided.

The tibia is thus divided into three parts, as shown
in the diagram (Fig. 64), the central
portion being occupied by the two
tracheze (Tig. 64, tv, tr).

Of the other two spaces, one (the
lower one in the figure) is occupied
by the muscles, nerves, etc., while
the other is mostly filled with blood,
which thus surrounds and bathes the
= auditory vesicles and rods (ar).

Fig. 64.—Section through The acoustic nerve—which, next
eee Ce) 2 te the optic, is the thickest in the
trachew? ar the awa, Dody—divides soon after entering
ye the tibia into two branches; the one

forming almost immediately a ganglion, the supra-

tympanal ganglion, to which I shall refer again pre-
sently; the other passing down to the tympanum,
where it expands into an elongated flat ganglion, known

after its discoverer as the organ of Siebold (Hig. 65),

and closely applied to the anterior trachee.

STRUCTURE OF EAR. 103

It is well shown in Fig. 65, taken from Graber. At
the upper part of the ganglion is a group terminating
below in a single row of vesicles, the first few of which

fy }H,
|

2
\@}

ial

139000.

Fig, 65.—The trachee and nerve-end organs from the tibia (leg) of a grasshopper
(Ephippigera vittum) ; after Graber. EBI, Terminal vesicles of Siebold’s organ ;

AT, hinder tympanum ; Sp, space between the trachee; AZ, hinder branch of the

; trachea; SW, nerves of the organ of Siebold; go, supra-tympanal ganglion;
Gr, group of vesicles of the organ of Siebold; vN, connecting nerve-fibrils between

the ganglionic cells and the terminal vesicles; So, nerve terminations of the organ

of Siebold; v7, front tympanum ; v7, front branch of the trachea.

are approximately equal, but which subsequently
diminish regularly in size. Each of these vesicles is

connected with the nerve by a fibril (Fig. 65, vN), and
contains an auditory rod (Fig. 66).

104 AUDITORY RODS..

One of these auditory rods is shown in Fig. 66,
and the general arrangement is shown in the subjoined
diagrammatic figure (Fig. 67). The rods
were first described by Siebold, who con-
sidered them to be auditory from their
association with the stridulating organs.
They have since been discovered in
many other insects, and may be_re-
garded as specially characteristic of the
acoustic organs of insects. ‘They are
brightly refractive, more or less elon-
gated, slightly club-shaped, hollow (in
which they differ from the retinal rods),
and terminate, in Graber’s opinion,* in
_ @ a separate end-piece (Fig. 66,40). In
ae Ber c ghee! different insects, besides being in some

vinulissimus (after CASES MOFe elongated than in others,
Graber, Fig. 90). ° . :

fil, Auditory rod; they present various minor modifica-
Ho, Serminal Piece tions in form, but are nearly uniform in
size—about ‘016 mm.; being as large, for instance, in
the young larva of a Tabanus (2 mm. long) as in
much larger insects. ‘They are, as we shall see, widely
distributed in insects, but as yet unknown in other
animals.

At the upper part of the tibial organ of Ephippigera
there is, as already mentioned, a group of cells, and
below them a single row (Fig. 65) of cells gradually
diminishing in size from above downwards. One can-
not but ask one’s self whether the graduaily diminish-
ing size of the cells in the organ of Siebold (Fig. 66)
may not have reference to the perception of different

* Graber, “ Die chordotonalen Sinnesorgane und das Gehor der
Insekten,” Arch. fiir Mic. Anat., 1882.

POSITION OF AUDITORY RODS. 105

notes, as is the case with the series of diminishing
arches in the organ of Corti (ante, p. 80) of our own ears.

I have already alluded to the supra-tympanal
ganglion; this also terminates in a number of vesicles

Fig, 67.—Diagram of a section through the auditory organ of a Grasshopper (Meco-
nema). ¢, cuticle; a.7, auditory rod; a.¢, auditory cell; tr, tracher.

containing auditory rods, which are said to be somewhat
more elongated than those in the organ of Siebold.

The arrangement of the organ is very curious, and
will best be understood by reference to Fig. 68.

The great auditory nerve, as already mentioned,
bifurcates almost immediately after entering the tibia,
and one of the branches swell into a ganglion: from
this ganglion proceed fibres which enlarge into
vesicles (Fig. 68), each containing an auditory rod; and
then again contract, approximate into a close bundle,
and coalesce with the hypoderm (inner skin) of the
wall of the tibia. The supra-tympanal organ of the
crickets closely resembles that of the grasshoppers,
while, on the other hand, they appear entirely to want
the organ of Siebold (Fig. 65). This is a very rematk-
able difference to exist in two organs otherwise so
similar,

There appear to be two ways in which the atmospheric

106 EAR OF LOCUSTS.

vibrations may be communicated to the nerve: either
the vibrations of the tympanum may act upon the
air in the trachez, and so upon the auditory rods, or
the air in the tracheze may remain passive, and the
vibrations may act upon the auditory rods through the
fluid in the anterior chamber of the leg. The fact
that the auditory rod is turned away from the tracheze
would seem to favour this hypothesis.

Fig. 68.—Outer part of a section through the tibia of a Gryllus viridissimus (after
Graber). A, Hind surface of leg; p, wall of trachea; F, tat bodies; Su, suspensor
of the trachea; vW, tracheal wall; TN, nerve; gz, ganglionic cells; 7B, tissue
connecting the ganglionic cells; £.Sch., end tubes of the ganglionic cells, each
containing an auditory rod; fa, terminal threads of ditto.

In the true Locustide (Acridiodee of Graber) the
organ of hearing is situated, not in the anterior tibia,
but in the first segment of the abdomen ; externally it is
marked by a glistening appearance, and it is oval, orin
some cases nearly ear-shaped. It was first noticed by
Degeer. Behind the tympanum is a large tracheal sac,
as in the families already described, and the tension of
the tympanum is regulated by one, or in some cases by
two muscles. The tympanum also presents two chitin-

EAR OF LOCUSTS. 107

ous or horny thickenings, a small triangular knob, and
a larger, somewhat complicated piece, consisting of two
processes—a shorter upper, and a longer lower one,
making a broad angle with one another.

As in the preceding families, so also in the
Locustidz, the acoustic nerve is in close connection
with the tracheze ; it swells into a ganglion, which con-
tains in some species as many as 150 auditory rods, and
then, as in the supra-tympanal organ (see p. 105), con-
tracts into a tapering end, which is attached to the small
chitinous knob. ‘The auditory rods differ in no respect,
as yet ascertained, from those already described.

For many years no structure corresponding to the
tibial auditory organ of the Orthoptera was known in
any other insect.

In 1877, however, I discovered * in ants a structure
which in some remarkable points resembles that of the
Orthoptera, and which I described as follows :—“ The
large trachea of the leg (Fig. 69) is considerably

S

Ci ZL
WN AN ON

Li
Zea

— = Tt KS
» NY ONCE SS
——

Fig. 69.—Tibia of yellow ant (Lasius flavus), x 75. 8, S, Swellings of large trachea;
rt, small branch of trachea; x, chordotonal organ.

swollen in the tibia, and sends off, shortly after entering
the tibia, a branch which, after running for some time
parallel to the principal cee joins it again.

“Now, I observed that in many other insects the

* Lubbock, “On the Anatomy of Ants,” Microscopical Journai,
1877.

108 PECULIAR STRUCTURE IN LEG OF ANT

tracheze of the tibia are dilated, sometimes with a
recurrent branch. ‘The same is the case even in some
mites. I will, however, reserve what I have to say on
this subject, with reference to other insects, for another
occasion, and will at present confine myself to the ants.
If we examine the tibia, say of Lastus flavus, we shall
see that the trachea presents a remarkable arrange-
ment (Fig. 69), which at once reminds us of that which
occurs in Gryllus and other Orthoptera. In the femur
it has a diameter of about 3,55 of an inch; as soon,
however, as it enters the tibia, it swells to a diameter
of about =45 of an inch, then contracts again to gl),
and then again, at the apical extremity of the tibia,
once more expands to 33,5. Moreover, as in Gryllus,
so also in Formica, a small branch rises from the upper
sac, runs almost straight down the tibia, and falls
again into the main trachea just above the lower sae.

“The remarkable sacs (Fig. 69, S, S) at the two
extremities of the trachea in the tibia may also be well
seen in other transparent species, such, for instance, as
Myrmica ruginodis and Pheidole megacephala.,

“ At the place where the upper tracheal sac contracts
(Fig. 69) there is, moreover, a conical striated organ (a),
which is situated at the back of the leg, just at the
apical end of the upper tracheal sac. The broad base
lies against the external wall of the leg, and the
fibres converge inwards. Indications of bright rods
may also be perceived, but I was never able to make
them out very clearly.”

This closely resembles both in structure and position
the supra-tympanal auditory organ of the Orthoptera.

Graber has entirely confirmed this account and dis-
covered some insects in which the structure is more

ORIGIN OF EAR. 109

clearly visible than in any which I had examined.
Fig. 70 represents part of the tibia of Lsopteryx apicalis.
These organs do not, however, appear to be univer-
sally present. In some very transparent species no
trace of them can be found.
But though so similar in structure, and probably in

Fig. 70.*—Part of the tibia of Isopteryx apicalis (after Graber). Sc, Auditory organ;
ef, terminal filament; Cu, cuticle; G, ganglion cells; ef, terminal filaments; tr,
trachea; m, nerve.

function, it may be doubted whether this tibial organ
in the ants can be traced to acommon origin with that
of the Orthoptera. According to Graber, the direction
of the rods is reversed in the two cases, which he regards
as clear proofs that they have arisen independently.
He is even of opinion that the tympana themselves
have originated independently in the different groups
of Orthoptera. Moreover, Graber has found this organ
In certain insects not only in the anterior, but also in
the two other pairs of legs. Indeed, rods of the same
character have been found in other regions of the body.

* Tn this, as in one or two of the other figures, the explanation of

some of the lettering appears to be omitted in the original. At least,
I have been unable to find it.

110

EAR OF FLY..

As long ago as 1764 Keller * observed that the base
of the curious club-like “halteres,” or rudimentary
hind-wings of flies, “est garnie de poils trés courts,
ou la tige a le plus d’epaisseur pres du corps; elle est

te

nit et
ARRAY
q j
a
i)
itt
Si
SY |
|
Nit
3 |

Vi
Wi
\

Wl
i \k
saa

| | | | ii
| fi

il
Hitt}
i
|

Fig. 71.—One of the

halteres of a fly

(after Lowne).

inflexible, et presque garrotté par en
haut de plusieurs nerfs; en un mot, elle
est faite de maniere que l’on peut juger
par sa force par les dehors.” This
observation remained unnoticed, and no
further description appears to have been
given of the organ until it was redis-
covered by Hicks in 1856, and more
fully described in 1857.7

He found that though in the Diptera
(flies and gnats) the hind wings are
reduced to two minute, club-shaped
organs, they still receive a nerve which

is the largest in the insect, except that

which goes to the eyes. This proves
that they must serve some important
function, and renders it almost certain
that they are the seats of some sense.
He also found at the base of the halteres
a number ot “ vesicles,” arranged in four
groups, and to each of which the nerve
sends a branch, though the mode of pre-
paration which he adopted did not

permit him to see the finer structure of the nerves,
which he figures as mere fine, hard lines. He describes
the “vesicles” as “thin, transparent, hemispherical, or

* « Geschichte der gemcinen Stubenfliege,” 1764. I have not seen
the original, and quote from Hicks’s paper.
+t Transactions of the Linnean Society, vol. xvii.

——*

ee

PECULIAR SENSE-ORGANS. 111

more nearly spherical projections from the cuticular
surface,’ and as placed in rows. The number and
arrangement differ in different species: the blowfly
(Sarcophaga carnaria) has ten rows, Syrphus luniger as
many as twenty.

These organs have recently been again examined by
Bolles Lee.* ‘The vesicles are, according to him, un-
doubtedly perforated, contain a minute hair, and those
of the upper groups are protected by hoods of chitine.
He inclines to correlate them with the similar antennal
organs, which he regards as olfactory. His view of the
minute structure of these rods differs from that of
previous authors, and the subject requires further
study.

He finds, moreover, that the sense-organ containing
the rods has nothing to do with the vesicular plates,
but that they are attached to the cuticle in a different
place, and where it presents no special modification.

The numerous small membranes in the halteres of
insects seem to bear somewhat the same relation to
the single tympanum of, say, the locust, as the many-
faceted eyes do to those with a single cornea. The
head of the halteres is divided into two separate
spaces by a membrane composed of elongated hypo-
dermal cells. The upper part contains a number of
large vesicular cells, like those which are in connection
with the ends of the trachee. It does not appear
to contain any special sense-organ, and, in fact, the large
nerve is almost entirely devoted to the sense-organs at
the base. M. Bolles Lee suggests that it perhaps
serves principally to regulate the pressure on these
delicate structures.

* “T.es Balanciers des Dipteres,” Recueil Zool. Suisse, 1885.

7

112 AUDITORY RODS IN BEETLES.

Special sense-organs occur also on the wings of other
insects. Hicks found them “ most perfect in the Diptera,
next so in the Coleoptera, rather less so in the Lepidop-
tera, but slightly developed in the’Neuroptera, scarcely
at all in the Orthoptera (though this assertion may be
hereafter modified), and that only a trace of them exists
in the Hemiptera.” They are similarly constituted and
equally developed in bothsexes. Hicks regarded them
as organs of smell. Leydig,* on the contrary, considered
them as auditory organs. His mode of preparation dis-
played better the structure of the nerves, and he found
that they end in peculiar, club-shaped rods (Stdbchen
oder Stafle), closely resembling those mm the ears of
Orthoptera. He observes that, as in the case of the
tibial auditory rods of Orthoptera these rods are of
two sorts, which are arranged separately, those in one
part of the organs being shorter and blunter, those in
another more pointed and elongated. Bolles Lee, on
the contrary, considers that the supposed existence of
two forms, pointed and rounded, is merely due to an
optical deception, and that in reality they are all
similar. Leydig also observed in some cases that the
rods were thrown into fine ridges. He found also
somewhat similar papille on the front wings of certain
insects, but could not detect in them the characteristic
nerve-ends. It must be confessed that the base of the
wing would not seem a convenient place for an organ
of hearing. The movements of the wing, it might
well be supposed, would interfere with any delicate
sensations. Still, this objection would apply to almost
any sense being thus placed.

“ Auditory rods” are now, moreover, known to occur

* Miiller’s Archiv., 1860.

‘ POSITION OF AUDITORY RODS. lia

in other parts of the body ; for instance, they have been
discovered in the antennze of a water-beetle (Dytiscus)
and of Telephorus by Hicks, Leydig, and Graber, and in
the body segments of several larve by Leydig, Tee
mann, Graber, Grobben, and Bolles Lee. In the larva
of Dytiscus, indeed, they have been observed in the
body, antenne, palpi, under lip, and legs. Moreover,
while, as we have seen, in the tibize of Orthoptera
and the halteres of flies they are numerous, in some of
these cases they are few, sometimes, indeed, only a
single rod being present, as discovered by Grobben in
Ptychoptera.* Nevertheless the evidence that they
are really acoustic organs is, in the case of the
Orthoptera, so strong, ‘their structure is so peculiar,
and the gradation of these organs from the most com-
plex to the most simple is so complete, that it seems
reasonable to attribute to them the same function. —
Moreover, as regards the very simplest forms there is
another consideration pointing to this conclusion. We
have seen that in the Orthoptera the terminal filaments
close up, and are attached to the skin. Now, it seems
to be a very general rule, in reference to these organs,
that they are attached to the skin at _two points,
between which is situated the attachment of the nerve.
These points, moreover, are so selected as to be main-
tained at the same distance from one another, thus pre-
serving an equable tension in the connecting filament.
Fig. 72, for instance, represents part of one segment
of the body of the larva of a gnat (Corethra). This larva
is as transparent as glass, and very common in ponds,
a most beautiful and instructive microscopic object.
EG is the ganglion; a is the nerve in question, which
* Sitz. der K. Akad. der Wiss. Wien, 1876.

114 CHORDOTONAL ORGAN OF GNAT-LARVA.

swells into a little triangular ganglion at g; from g
the auditory organ runs straight to the skin at e,
and contains two or three auditory rods (not, how-
ever, shown in the figure) at the point Chs; in the
opposite direction, a fine ligament passes from g to the

Fig. 72.—Right half of eighth segment of the body of the larva of a gnat (Corethra
plumicornis) ; after Graber. EG. Ganglia; , nerve; g, auditory ganglion;
gb. auditory ligament ; Chs, auditory rods; a, auditory nerve; é, attachment oi
auditory organ to the skin; 0, attachment ‘of auditory ligament to the skin;
hn, hn’, termination of skin-nerve ; tb, plumose tactile hair; h, simple hair;
tg, ganglion of tactile hair; 7m, longitudinal muscle.

skin at b. Hence the organ ge is suspended in a

certain state of tension, and is favourably situated to

recelve even very fine vibrations.*

There are, as we have seen, a large number of
observations which point to the antenne as organs of
hearing, and many more might have been given.
When we come to consider, however, the anatomical
provision which renders the perception of sound

* Similar organs occur in other insects, as, for instance,in Ptychoptera.

AUDITORY HAIRS ON ANTENNZ OF GNAT. 115

possible, we are met by great difficulties. The evidence
is, I think, conclusive that the antenne are olfactory
as well as tactile organs, and I believe that they serve
also as organs of hearing. There are, moreover, as
shown in the last chapter, various remarkable structures
in the antenne, and I have given reasons for thinking
some of them to be the seat of the sense of smell.
Which, if any, of the remainder convey the sense of
sound, it is not easy to determine. I have suggested
that Hicks’s bottles (Fig. 48) may act as microscopic
stethoscopes ; * but they occur, so far as we at present
know, only in ants and certain bees.

Fig. 73.—Head of gnat.

That some of the antennal hairs are auditory can,
‘I think, no longer be doubted. Johnson, whose figure
I give (Fig. 73), suggestedt in 1855 that the hairs on
the antenne of gnats serve for hearing. Mayer also,t

* I am glad to see that Leydig, who, however, does not appear to have
read either Hicks’s paper or mine, also regards these as chordotonal
organs (Zool. Anz., 1886).

tT Quarterly Journal of Microscopical Science. 1855.

t American Journal of Science and Arts, 1874.

116 SYMPATHETIC VIBRATIONS.

led by the observations of Hensen, has made similar
experiments with the mosquito, the male of which has
beautifully feathered antenne. He fastened one down
on a glass slide, and then sounded a series of tuning-
forks. With an Ut, fork of 512 vibrations per second
he found that some of the hairs were thrown into
vigorous movement, while others remained nearly
stationary. The lower (Ut;) and higher (Ut;) harmo-
nics of Ut, also caused more vibration than any
intermediate notes. These hairs, then, are specially
tuned so as to respond to vibrations numbering 512
per second. Other hairs vibrated to other notes,
extending through the middle and next higher octave
of the piano. Mayer then made large wooden models
of these hairs, and, on counting the number of vibra-
tions they made when they were clamped at one end
and then drawn on one side, he found that it “ coincided
with the ratio existing between the numbers of vibrations
of the forks to which co-vibrated the fibrils.” It is
interesting that the hum of the female gnat corresponds
nearly to this note, and would consequently set the
hairs in vibration.

Moreover, those auditory hairs are most affected
which are at right angles to the direction from which
the sound comes. Hence, from the position of the
antenne and the hairs, a sound will act most intensely
if it is directly in front of the head. Suppose, then,
a male enat bears the hum of a female at some little
di-tance. Perhaps the sound affects one antenna more
than the other. He turns his head until the two
antenne are equally affected, and is thus able to
direct his flight straight towards the female.

The auditory organs of insects, then, are situated in

ORGANS OF HEARING IN VARIOUS PARTS OF BODY. 117

different insects in different parts of the body, and
there is strong reason to believe that even in the same
animal the sensitiveness to sounds is not necessarily
confined to one part. In the cricket, for instance, the
sense of hearing appears to be seated partly in the
antenne, and partly in the anterior legs. In other
cases, as in Corethra, the division appears to be carried
still further, and a “ chordotonal” organ occurs in each
of several segments.

No doubt the multiplication of complex organs, like
our ears, arranged as they are to appreciate a great
variety of sounds, would be so great a waste that any
theory implying such a state of things would be quite
untenable; but with simple organs, such, for instance,
as that of Corethra* (gnat; Fig. 72), the case is
different, and there would seem to be an obvious
advantage in such organs occurring in different parts
of the body, ready to receive sound-waves coming from
different directions. Moreover, the different organs
exist; they do not appear to be organs of touch, yet
they are clearly organs of sense, and that sense, what-
ever it be, whether hearing or any other, and though
it may well be simple, and even perhaps confused,
must be seated in various parts of the body. The fact
of their being so distributed does not make it more
improbable that they should be organs of hearing, than
of any other sense.

At the same time, it is an interesting result of recent
investigations that the auditory organs of insects are
not only situated in various parts of the body, but are
constructed on such different principles.

* Where, however, the number does not approach to that in certain
Medusz (see ante, p. 84).

CHAPTER VI.
THE SENSE OF SIGHT.

It might at first sight seem easy enough to answer the
question whether an animal can see or not. In reality,
however, the problem is by no means so simple. We
find, in fact, every gradation from the mere power of
distinguishing a difference between light and darkness
up to the perception of form and coluur which we
ourselves enjoy.

The undifferentiated tissues of the lower animals,
and even of plants, are, as we all know, affected in a
marked manner by the action of light.

But to see, in the sense of perceiving the forms of
objects, an animal must possess some apparatus - by
means of which—firstly, the light coming from different
points, a, b, ¢, d, e, etc., is caused to act on separate
parts of the retina in the same relative positions; and
secondly, by means of which these points of the retina
can be protected from the lhght coming in other
directions.

There are three modes in which it is theoretically
possible that this might be effected.

Firstly, let S S’ be an opaque screen, with a small
orifice at o. Let abede be a body in front of the

THREE POSSIBLE MODES OF SIGHT. 119

screen. In this case the rays from the point ¢ can
- pass straight through the orifice 0, and fall on the
retina of an eye, or on a flat surface atc’. There is
no other direction in which the rays from ¢ could pass
through o. In the same way,
the light from a would fall on
the point a’, that from 0 on 0’,
from d on d’, and eon é.

The resuits which would be
given in this way would be,
however, very imperfect, and,
as a matter of fact, no eye con-
structed on this system is
known to exist.

Secondly, let a number of
transparent tubes or cones with opaque walls be ranged
side by side in front of the retina, and separated from
one another by black pigment. In this case the only
light which can reach the optic nerve will be that which
falls on any given tube in the direction of its axis.

»> Qa nae
Rane gt

Fig. 74.

Fig. 75.

For instance, in Fig. 75 the light from a will pass to a’,
that from 0 to 0’, that from e¢ to ¢’, and so on. The
light from ¢, which falls on the other tubes, will not

120 DIFFERENT FORMS OF EYE.

reach the nerve, but will impinge on the sides and be
absorbed by the pigment. Thus, though the light
from ¢ will illuminate the whole surface of the eye, it
will only affect the nerve at ¢.

In this mode of vision, which was first clearly
explained by Johannes Miller, the distinctness of the
image will be greater in proportion to the number ot
separate cones. “An image,” he says,* “formed by
several thousand separate points, of which each corre-
sponds to a distinct field of vision in the external
world, will resemble a piece of mosaic work, and a
better idea cannot be conceived of the image of
external objects which will be depicted on the retina
of beings endowed with such organs of vision, than by
comparing it with perfect work of that kind,”

There is, it will presently be seen, reason to suppose
that the compound eyes of insects, crustacea, and
some molluscs, are constructed on this plan.

Thirdly, let L (Fig. 76) be a lens of such a form

Fig. 76.

that all the light which falls upon its surface from the
point a is re-collected at the point a’, that from 6 at U’,
from ¢ at c',and so on. If nowother light be excluded,

* « Phys. of the Senses,” by Johannes Miller, translated by Dr.
Baly.

THE VERTEBRATE EYE. 121

an image of a 4c will be thrown on a screen or on a
retina at a’ b'c’. The image, it will be observed, is
necessarily reversed. ‘This is the form of eye which
we possess ourselves: it is, in fact, a camera obscura.
It is that of all the higher animals, of most molluscs,

the ocelli of insects, etc.
Fig. 77, taken from Helmholtz, will give an idea of

the manner in which we see.

—s
SS
AN
SS * PA —_
SS J
=
=
=S>=
S —
= =
= =
- G -
= SS
= =
= Ss
— SS
—="" =
SS
=> _ SS
SAK / gS
Sa i ASS
rk —E—SSsSssSsSs~
di | aii SSS
Wi i | Hy i SSS
PULA =
vipa Fi 8
(iil

Fig. 77.—G, Vitreous humor; L, lens ; W, aqueous humor; ¢, ciliary process; d,
optic nerve; € €, Suspensory ligament; k k, hyaloid membrane; f f, h h, cornea;
9 g, choroid; 2, retina; 1 /, ciliary muscle: mf, nf, sclerotic coat; p p, iris; s,

the yellow spot.
The eyeball is surrounded by a dense fibrous mem-
brane, the sclerotic coat, or white of the eye, mf, nf, which

122 STRUCTURE OF THE: EYE.

passes in front into the glassy, transparent cornea, f f,
hh; the greater part of the centre of the eye is occupied
by a clear gelatinous mass, the vitreous humor, G, in
front of which is the lens, L ; while between the lens and
the cornea is the aqueous humor, W. The sclerotic
coat is lined at the back of the eye by a delicate,
vascular, and pigmented membrane—the choroid, g g, so
called from the great number of blood-vessels which it
contains ; in front this membrane joins the iris, p y,
which leaves a central opening, the pupil, so called
from the little image of ourselves, which we see re-
flected from an eye when we look into it. The iris gives
its colour to the eye, its posterlor membrane con-
taining pigment-cells; if these are few in number, it
appears blue, from the layer behind shining through,
and the greater the number of these cells the deeper
the colour. e e, is a peculiar membrane, which serves to
retain the lens in its place. ‘The optic nerve, d, enters
at the back of the eye, and, spreading out on all sides,
forms the retina, 2, of which one spot, s, the yellow spot,
is pre-eminently sensitive. The action of the eye re-
sembles that of a camera obscura, and, as shown in
Fig. 76, the rays which fall upon it are refracted so
as to form a reversed picture on the back of the eye.

The retina (Fig. 78) is very complicated, and,
though no thicker than a sheet of thin paper, consists
of no less than nine separate layers, the innermost
(Figs. 78, 79) being the rods and cones, which are the
immediate recipients of the undulations of light.
Fig. 79 represents the rods and cones isolated and
somewhat more enlarged.

The number of rods and cones in the human eye is
enormous. Ata moderate computation the cones may

THE RETINA. 135

be estimated at over 3,000,000; and the rods at
30,000,000.*

D
Piro
5 <

REY OOF
20 O20 ©,
032.
on
On So oh
\ ao! , %!
&
Fede Se8 Proee’oh |
=) 8 be 7g
Ae
C0 QS
30 SP, 9

is

5,
RAs: c
a

sO 969 7

1
e
9
—we, ©.
i”?
0 ar
1g 2%,
200 &:
19 BErLOES
OOK
v.
5.8
oO

ROY
EXD,
OU |
12)
“97.0

Fig. 78.—Section through the retina (after Max Schultze). Beginning from the outside,
1, limitary membrane; 2, layer of nerve-fibres ; 3, layer of nerve-celis; 4, nuclear
layer; 5, inner nuclear layer; 6, intermediate nuclear layer; 7, outer nuclear
layer ; 8, posterior membrane; 9, layer of small rods and cones; 10, choroid.

* Sulzer estimates the cones at 3,360,000; Krause places the cones
at 7,000,000, the rods at 130,000,000; but Professor M. Foster tells me
that he thinks the latter figure is too high.

124 THE RODS AND CONES.

It will be observed that the nerve does not, as one
might naturally have expected, enter the eye and then
spread itself out at the back of the retina; but, on the
contrary, pierces tle retina
and spreads itself out on the
front, so that the cones and
rods look inwards, and not
outwards—towards the back
of the eye, and not at the
object itself. In fact, we do
not look outwards at the
actual object, but we see the
object as reflected from the
base of our own eye.

From the arrangement of
the rods in the eyes of verte-
brata, then, the light has
necessarily to pass through
the retina, and is then re-
flected back on it. This
involves some loss of light;
on the other hand, it perhaps
‘ secures the advantage that
/“\weeq the sensitive terminations of
: sez the rods and cones can be

SReeseS gaec5e: ; : =
Fig. 79.—A, Inner segments of rods more readily supplied with

(s, S, S) and cones (z, 2’) from man,
the latter in connection with the blood.

cone-granules and fibres as far as I do not propose to enter

the external molecular layer, 6. In

the interior of the inner segment of 4 =

both rod and cone fibrillar secbene into the reason for this

wea ee peculiar arrangement, which
is connected with the development of the eye. Bat
it is so different from what might have been expected,

is in itself so interesting, and makes so important a

THE BLIND SPOT IN THE EYE. 125

eontrast with the form which is general, though not
universal among the lower animals, that I think it
will not be out of place to
mention a very simple and
beautiful experiment by
which every one can satisfy
himself that it is so.

One result is that we have
in each eye a blind spot, that
at which the nerve enters.
Turn the present page, so
that the white circle is in
front of the left eye and the
small cross in front of the
right. Then close the right
eye, look steadily across at
the cross with the left,
and move the book slowly
backwards and _ forwards.
At one particular distance,
about ten inches, the white
eircle will come opposite
the blind spot and _ will
instantaneously <lisappear.
Across an ordinary room, if
a man stands in front of a
_ sereen, his head may in the
same way be made entirely
to vanish.

The ordinary vertebrate
eye consists of two main runes ee
divisions: the refractive Fig. 80.
part, which is a modified portion of the skin; and the

126 INVERSION OF THE: RODS.

receptive part, which arises from the central nervous
system; and the inverted arrangement of the rods is,
we can hardly doubt, connected with the develop-
ment of the eye, though it is not yet, I think, satis-
factorily explained. |

There is, however, another eye in vertebrates, with
reference to which { must say something, and which,
though now rudimentary, is most interesting. Our
brain contains a small organ, about as large as a hazel-
nut, known, from its being shaped somewhat like a cone
of a pine, as the pineal gland. Its function has long
been a puzzle to physiologists. Descartes suggested
that it was perhaps the seat of the soul; and though
this idea, of course, could not be entertained, no
suggestion even plausible had been made.

So matters stood until quite recently, when a most
unexpected light has been thrown upon the question.
As long ago as 1829, Brandt, describing the skull of
a lizard (Lacerta agilis), pointed out that in the
centre of the top of the head was a peculiar spot, one
of the scales being quite unlike the rest. Leydig *
subsequently observed that on the head of the slow-
worm (Angwis fragilis) there is a dark spot surrounding
a small unpigmented body immediately over the pineal
gland. Rabl-Rickhard,t in 1884, again called atten-
tion to this structure, and suggested that it might
serve for the perception of warmth. Ahlborn,{ in the
same year, was the first to suggest that it was a
rudimentary eye. De Graaf§ has the merit of dis-

* «Die Arten der Saurier.”’ |

t “ Entw. des Knochenfischgehirn,” Bericht der Sitz. naturf. Freunde.
Berlin: 1882.

t “Ueber d. Bedeutung der Zirbeldriise,” Zett. fiir Wiss. Zool., 1884.

§ “Zur. Anat. und Ent, der Epi.b. Amphihbien und Reptilien,” Zool.
Anz., 1886.

THE PINEAL GLAND. 127

covering that in the slow-worm the pineal gland is
actually modified into a structure resembling an inver-
tebrate eye. This remarkable structure has since been
examined in various Reptilia by Mr. Spencer.* It
appears to be more highly organized in Hatteria than
in any other form yet studied; but the retrogression of
the different structures has not proceeded pari passu,
in some cases the lens, in some the retina, in others
the nerve, having been most modified, or having dis-
appeared. In Hatteria and Varanus the eye is very
distinct; the interior parts being more perfect in the
former; while in the latter it is externally most con-
spicuous, standing out prominently from its creamy
whiteness. ‘The lens is cellular in structure, aud thins
away rapidly at the sides. The “rods” are well
developed, and embedded in pigment.

Spencer describes the various modifications of the
organ in the iguanas, chame-
_leons, flying lizards, geckos, ete.

Fig. 81 represents the ex-
ternal aspects of the eye-scale
in a small lizard (Calotis), with
the transparent cornea in the
middle, through which the eye
is seen; and the diagram
Fig. 82 a section through
the eye-scale of a small lizard
(Lacerta). Fig. 81.— Pineal spt feale on the

A very interesting point in bead es (Caloh
connection with the pineal eye
consists in the fact that the optic nerve does not
penetrate the retina, and then spread out on its outer

* Quarterly Journal of Microscopical Science, October, 1886.

128 THE RUDIMENTARY MEDIAN EYE.

surface, as in the lateral eyes of all vertebrates, but, on
the contrary, is distributed over its exterior surface. It
is, therefore, as De Graaf pointed out, formed in this
respect on the type of the usual invertebrate eye; so
that we have the remarkable fact that in the same

Fig. 82.—Diagram of a section through the skull and pineal eye of Lacerta viridis.
C, Cuticle; Pa, parietal bone; Hp, epidermis; Z, lens; Pig, Pigment; R, rete
muscosum ; CH, cerebral hemisphere; 1, nerve; £.p, epiphysis; OpL, optic lobe
of brain.

vertebrate animal we find eyes formed tn two different
types. Not only so, but the development is dissimilar,
the lens of the pineal eye being formed out of the
walls of the neural canal. So that the lens of the
pineal eye is a totally different structure from that of
the lateral eyes.

Spencer observed no effect whatever when he threw

a strong light on the pineal eye. In fact, he does not
believe that in any of the species examined by him
the organ is at present in a functional condition.
Indeed, in some cases the cornea is quite opaque, and
in others the nerve to the brain is not continuous; so
that there can be no vision. At the same time, it
seems to be established that this organ is the degraded
relic of what was once a true eye.

From the size of the pineal orifice in the skull of

7 iS ee

SA A? #~

Be Ne fi

THE MEDIAN VERTEBRATE EYE. 129

the huge extinct reptiles, such as Ichthyosaurus and
Plesiosaurus, it has been, | think, fairly inferred that
the pineal eye was much more developed than in any
known living form.

In living fish and Amphibia, so far as they have been
yet examined, the organ is even more rudimentary
than in reptiles. But in the fossil Labyrinthodonts the
skull possesses a large and well-marked orifice for the
passage of the pineal nerve. This orifice is, in fact,
so large that it can scarcely be doubted that the eye in
these remarkable amphibia was also well developed,
and served as a third organ of vision.

In birds the organ is present, but retains no re-
semblance to an eye. It is solid and highly vascular.
In mammals it is still more degenerate, though a trace
is still present even in man himself.

The larval Ascidians, which present so many points
of resemblance to the lowest vertebrates, and especially
to the Lancelet (Amphioxus), have hitherto been re-
garded as differing from them in the possession of a
central eye. It now, however, appears that the verte-
brate type did originally possess a central eye, of which
the so-called pineal gland is the last trace.

It seems, then, very tempting to regard the pineal
eye as representing the central eye of Amphioxus;
but Spencer points out that the two organs differ
greatly in structure, and he himself doubts whether
the pineal eye is really the direct representative of the
central eye in the Tunicata.

Béraneck* also regards the pineal as entirely
different from the central eye of the Tunicata. Indeed,
he considers its differentiation as an eye to be a

* “Ueber d. Parietal Auge der Reptilien,” Jenaische Zeit., 1887.

130 ORGANS OF VISION IN THE LOWER ANIMALS.

secondary modification, and considers that it had
previously served some other function.

However this may be, it cannot be doubted that the
pineal gland in Mammalia is the representative of the.
cerebral lobe which supplies the rudimentary pineal
eye of Reptilia, and this itself is probably the degenerate
descendant of an organ which in former ages performed
the functions of a true organ of vision.

Toe ORGANS OF VISION IN THE LOWER ANIMALS.

Mere sensibility to light is possible without any
optical apparatus. Even plants, as we know, can well
distinguish between light and: darkness; and though
it seems that in our own case the general surface of
the skin has lost its sensitiveness to light, still, in many
of the lower animals, light seems to act generally and
directly on the tissues.

Some microscopic vegetable forms even, as, for in-
stance, Englena (Fig. 83), possess a red spot,* which

___-—. appears to be specially sensi-

ee we Me tive to light.

The lower animals are, in

= a great many cases, very

transparent. Light passes

Fig. 83.—Englena viridis. easily through them, and,
e, Eye-spot.

except in so far as it is ab-
sorbed, can hardly be supposed to produce any effect.
The most rudimentary form of a light-organ, then, may
be considered to be a coloured spot.

In the first chapter I have endeavoured to show how

* The moving zoospores of certain algze also possess a red spot,
which may perhaps have special reference to light.

COLOR-SPOTS. 131

it may be possible to trace an almost complete series
from such a mere spot of colour in the skin up to a
complex organ of vision, such, for instance, as that of
a snail; indeed, in the development of the eye in the
individual animal may be traced some of the same stages
as have probably been passed through by the ancestral
forms of the animal itself in long bygone ages.

We must not, however, suppose that all eyes can be
traced back to one and the same origin, or have been
developed in the same manner. ‘There are even cases
in which an organ fulfilling a different function appears
to have been modified into an eye.

Look, for instance, at the organ of touch of
Onchidium* (Fig. 16). The cuticle (see p. 14) is
thickened into a biconvex, almost lens-like body; the
epithelial cells are elongated, and below is a mass of
cells, to which runs a nerve. A very little change
would make this an organ capable of distinguishing
light from darkness, and
some of the eyes of On-
chidium appear, indeed,
to have thus originated.

Compare with this, for
instance, the ocellus of
the young larva of a
water-beetle (Fig. 84),
as figured by Grenacher. —

The eye-spots of Me- “S'yoing bytiscus larva (after Grenacher).
dusm were first noticed — ;Lomttens; 9 cells orming the wtreous
by Ehrenberg in 1836, “™
and the lens was discovered many years afterwards by
de Quatrefages. It is, in fact, by no means universally

* A slug-like genus of molluscs.

132 ECHINODERMS.

present; the eye, if so it can be called, in many species
consisting merely of a coloured spot, while in others
it is entirely absent.*

Fig. 85.—Eye-spot of Lizzia (after Fig. 86.—Eye-bulb of Astropecten (after
Hertwig). oc, Ocellus; 7, lens. Haeckel).

In the Echinoderms, the eyes, which were discovered
by Ehrenberg, have been described by Haeckel,f
Wilson, Lange, and others.§ They are in some cases
situated, as in Astropecten, on a pear-shaped bulb
(Fig. 86). )

They consist of a lens (Fig. 87), supplied with a

nerve, and lying in a mass of pigment. In Solaster or

* Allman, “ Mon. of the Hydroids,” Ray Society, 1871.

+ “Ueber die Augen und Nerven der Seesterne,”’ Zeit. fiir Wiss., vol. x.

t Transactions of the Linnean Society.

§ Lange, “Beit. z. Anat. und Hist. der Asterien und Ophkiuren,”
Morph. Jahrbuch, 1876.

WORMS. 133

Asteracanthion the lenses look like brilliant eggs,
“each in its own scarlet nest.”

In some species there are as many as two hundred
eyes; but there appears to
be no retina, so that they
can do little more than dis-
tinguish between light and
darkness.

It is quite possible that in
some of the lower animals,
where the eye-spot is sup-
posed to consist merely of a
layer of pigment at the end
of a nerve, a lens may here-
after be discovered.

In the Turbellaria* the PERN a cities ge nee
eyes, which were first noticed pickae ett
by de Quatrefages, are numerous, and le immediately
under the epithelium (skin), They consist of a certain
number of crystalline rods and corresponding retinal
cells, resting on a cup-shaped bed of pigment, and con-
nected with a nerve. ‘There is often a group on each
side of the head, immediately over the brain. In
species which possess tentacles the eyes are generally
combined with them ; in others they are scattered over
the whole periphery of the body, and look in all direc-
tions. They differ greatly in size, and in the number
of rods and retinal cells—the larger tentacular eyes
having several; the small, scattered ones, which are

generally more deeply situated, even as few as two or
three.

* “Die Polycladen,” Fauna und Flora des Golfes von Neapel, 1884.
Carriere, “ Die Augen von Planaria,” Arch. fiir Mic. Anat., 1882.

134 WORMS.

In most of the Annulata (worms), the eyes, so far as
they have yet been described, are very simple, and
probably in most cases not capable of giving more than
a mere impression of light. In some species the eye-
spot is merely a group of pigmented epithelial cells.
In many (Fig. 87) there is, besides the pigment, a
well-marked lens. At the same time, it is probable
that in some cases this supposed simplicity is more
apparent than real. The dioptric part is often cellular,
consisting sometimes of one cell, sometimes of several.
They are generally, but not always, situated on the
head. The Polyophthalmians (Fig. 90), as already
mentioned, have a series along the sides of the body,
in pairs from the seventh to the eighteenth segments.
I agree with Carriére that there is no sufficient reason
for considering the supposed “eyes” of the leech as
organs for the perception of light, but other species
of the same group cClepstne) possess well-marked,
though rudimentary eyes.*

Certain leeches—tfor instance, Pas respirans—in
addition to the pigmented spots on the head, have also
some on the posterior sucking disc. ‘These somewhat
resemble the supposed organs of touch, but are larger,
and surrounded by pigment. ‘There is no lens, but the
large cells are very transparent. It is not supposed
that they give any distinct image, or can do more. than
distinguish light from darkness—as Leydig says,
“feel” the light. Still, I must confess that the deter-
mination of these curious organs as eyes seems to me
very doubtful.

Fig. 88 represents the anterior extremity of a small
freshwater worm (Bohemilla).

* Graber, “ Morph. Unt. itiber die Augen der frei-lebenden Borsten-
wiirmer,” Arch. fiir Mic. Anat., 1880.

WORMS. 135

Fig. 89 represents an eye-dot of Nereis. In this
genus there are two pairs of eyes, which differ some-

Fig. 88.—Anterior extremity of a freshwater worm (BSokemilla comata); after

— on ras ae brain, c, cuticle; Ap, hypoderm; Jb, tactile hair ;
what in structure, the lens in the anterior pair being
flatter, that in the posterior more conical. in Hesione
the difference is even more
marked.t In Polyophthalmus,
besides the eyes 1n the head,
there is, as already mentioned,
a series: alone the sides ci
the body, which differ some- Fig. 89.—Eye-dot of Nereis (after
Geet a structure from those MUI. tved sn ae to show
in the head. Lean

As a general rule, in the Annelids each eye contains
a single lens, but the cephalic eyes of Polyophthalmus,
according to Mayer, contain three.

ee Sys. und Morph. der Oligocheten.”
+ Graber, “Morph. Unt. iiber die Augen der frei-lebenden Borsten-
wurmer,” Arch. fiir Mic. Anat., 188.

8

136 WORMS.

SE. Stn!
= Sey £10.

Fig. 90.—Tke first twelve segments of Polyophthalmus pictus, seen from below (after
Mayer). The Roman numerals indicate the segments. St, Papille on the head;
KS, head; au, head eye; s.au, side eyes; Ol, upper lip; Ul, under lip; v.ph
pharyngeal vein; V.suwbinta, anterior ventral vein; V.d.l'—*, veins connecting the
superior lateral and vessels ; sept'—, intersegmentary membranes ; m.ocs.1, lateral
muscle of the esophagus; V.ann, pulsating circular vessel; Md.dr, stomach-
glands; V.v-l, vein connecting the inferior and lateral blood-vessels ; Md, stomach 5

Bm, muscles of the hairs; G, brain; jl.o, ciliated organ; qm, transverse muscle.

MOLLUSCS. . kee

: The most highly organized eyes in Annelids appear to

: be those of the Alciopide, which have been described
by Krohn,* de Quatrefages,t and especially by Greef }
and Graber.§ The Alciopide are small
sea-worms; they live principally in
the open sea, and, like many other
pelagic animals, are extremely trans-
parent. It is, indeed, often difficult
to see more of them than the two
very large eyes, red or orange, and a

~ pair of dark violet dots (the seg-
mental organs) on each ring.

tile f ait caged try “ na (tig

The principal parts of their eyes are ety
‘s —(1) the outer integument, the whole S eZ
of which issotransparentthatitneeds = FS
scarcely any modification; (2)the so- “4x =
Fe.

called “eye-skin,’ as to the true
nature of which there is still much
difference of opinion; (8) the lens; (4)
the “corpus ciliare ;” (5) the vitreous
humor; and (6) the retina, which
again 1s composed of four layers—(a)

fi Hig

, th ;
" Os RY : My
4, cea " tf {

How,

2

the rods; (b) pigment layer; (c) \
: granular layer ; (d) fibrous layer. His $4 Alciope Canter
In Mollusca the eyes are variously — *° @"°#8"*)

situated ; being, for instance, either placed on the pos-

terior tentacles; or between the feelers, as in the fresh-
’ water species; or on a short stalk at the side of the
: * “Zool. und Anat. Bemerk. iiber die Alciopeden,” Wiegmann’s
Arch., 1845. |

i + “ Ktudes s. 1. typ. Inf. de ’emb. deg Annelés,” Ann. Sct. Nat., 1850.

t “Unt. iiber die Alciopiden,” Nova Acta Acad. Leop. Carol.
vol. xxxix. 11, 1876.

§ Arch. fiir Mic. Anat., 1880.

oe 2. is ae
<< 7+ F.

~e i ae
ms a

138 MOLLUSCS.

feelers, as inthe Prosobranchiata; or on the back. In
some cases they are deeply sunk, even into the brain.

Fig. 92.—Perpendicular section through the eye-pit of a limpet (Patella); after
Carriére. 1, Epithelial cells; 2, retina cells, 3, vitreous body.

The mussels are generally deficient in eyes; and
some which are, as larve, provided with an eye, lose
their eyes when mature.

& “UP
mS SS.
=

Fig. 93.—EKye of Trochus magus (after Hilger).* Gl, Vitreous body ; No, nerve.

In the limpet (Patella),* on the outer side of the
tentacles, where the eyes are situated in more highly
organized species, are certain spots, which may be

* <¢Ryaisse. Ueber Molluskenaugen,” Zeit. fiir Wiss. Zool., 1881.
+ “Beit. zur Kennt. der Gastropodenaugen,” Gegenbaur’s Morph.

Jahrbuch, 1885.

af A ee Mon pea Oe TE

MOLLUSCS. 139

regarded as a very rudimentary organ for the per-
ception of light. ‘The skin is thrown into a pit, within
which the epithelial cells are elongated and pigmented.

In the sea-ear (Haliotis), and in Trochus (Fig. 98),
the arrangement is similar, but the depression is
deeper, the mouth is very much restricted, and the
interior is filled by a vitreous body.

In Murex (Fig. 94) the eye is still further developed,
and is entirely closed in, a lens being present.

Fig. 94.—Eye of Murex brandaris (after Hilger). L, Lens; Gl, vitreous body ;
No, nerve.

In the snail (Helix) the eye is still more highly
organized. It consists of a cornea, which lies imme-
diately below the skin; a lens, behind which is the
retina, consisting of three layers, (1) the rods, (2) a
cellular layer, (3) a fibrous layer. This, indeed, appears

140 CUTTLE-FISH..

to be a very general arrangement in the Mollusca.
The power of sight given by such an eye can be but
small. Indeed, it is probable that it does little more

Fig. 95.—Eye of Helix pomatia (after Simroth).* ct, Cuticle; a, epithelium ; b, cornea ;
c, envelope of the eye; d, cellular layer; e, fibrils of the optic nerve ; f, feeler
cell; na, nerve of the tentacle ; no, optic nerve.

than distinguish degrees of light. According to Lespes,

a Cyclostoma only perceives the shadow of a hand at a

distance of five inches, and a Paludina of eight.

It is interesting that, as Lankester first showed,f the
eye of Mollusca, in its gradual development, passes
through the stages which we find are the permanent
conditions in Patella and Haliotis, commencing as a
depression, which grows deeper and deeper, and
oradually closes over.

Even in the Nautilus the cornea leaves an opening,

* Simroth, “Ueber die Sinneswerkzeuge uns. einh. Weichthiere,”
Zeit. fiir Wiss. Zool., 1876.

+ “Obs. on the Dev. of Cephalopoda,” Quarterly Journal of Micro-
scopical Science, 1875.

COMPOUND EYES IN MOLLUSCS. 141

through which the water has free access to the interior
of the eye.

In the higher cuttle-fishes (Cephalopoda) the eye is

very complex, and the optic ganglion is in some cases
~ the largest part of the brain; but, while we find the
same parts, as, for instance, in Helix, though in a higher
state of development, there does not seem sufficient
reason to regard the two organs as homologous, but
it appears possible that the eye of the cuttle-fish had
an independent origin.

Certain bivalves (Lamellibranchiata) possess bright
spots round the edge of the mantle, or on the siphon,
which some naturalists maintain to be eyes, while
others deny them this character, ai their true
function, however, undecided.

But though there is much doubt in some cases, there
are other eye-spots which are certainly trne eyes. Of
these there are two distinct types—those of Spondylus,
Pecten, ete., on the one hand ; of Arca, Pectunculus, ete.,
on the other. The latter present several features of the
compound insect’s eye. This was first noticed by Will,*
and they have since been more fully described by
Carriere t and Patten.{ They are composed (Fig. 96)
of large conical cells with the points turned inwards.
Pigment is deposited in the periphery of the cells.
The outer surface is arched, and forms a biconvex lens.
These cells pass gradually into those of the ordinary
epithelium.

It will be most convenient to consider the mode in
which these compound eyes act when we come to

* < Ueber die Augen der Bivalven,” Frorieps Notizen, 1844.
tT “Die Sehorgane der Thiere,” 1885.
f£ “ Eyes of Molluses and Arthropods,” Miit. Zool. Stat. Neapel, 1886.

142 ARCA—SPONDYLUS.

consider those of insects, where they are more highly
developed.

The eyes of Pecten and Spondylus are, again, formed
on a totally different plan.

It has been already observed that there is an

Fig. 96.—Perpendicular section through an eye of Arca Noe (after Carriere). 1,
Epithelium of the edge of the man:le; 2, cells of vision; 3, lens; 4, 5, connective
tissue; 6, section of one of the ceils.

essential difference between the typical vertebrate and

the typical invertebrate eye; in that while in the

former, the optic nerve (Fig. 77) penetrates the retina
and then spreads out on the anterior suriace, so that
tiie “rods” point away from the light; in the normal
invertebrate eye, on the contrary, the nerve spreads
out on the back of the retina, so that the rods point
towards the light. Krohn,* however, made the remark-
able discovery that in the genus Pecten the rods, like
those of the vertebrates, are turned away from the light.

In this case, however, the optic nerve does not enter

the retina directly from behind, but runs round it and

passes, so to say, over the lip of the cup.
Here, then, we get a remarkable approach to the
vertebrate eye; but the similarity is still greater in

* Miiller’s Arch., 1840. See also Hensen, ‘‘ Ueber das Auge einiger
Lamellibranchiaten.” Zeit. fiir Wiss. Zool., 1805.

PECTEN. 143

Onchidium (a genus of slugs, widely spread over the
Southern Hemisphere), in which Semper has shown *
that the nerve actually pierces the retina as in verte-

=

yew =
= = PG
IR
SSS
SS

Fig. 97.—Diagram of eye of Pecten (after Hivkson). a, Cornea; 6, transparent base-
ment membrane supporting the epithelial cells of cornea; c, the pigmented
epithelium ; d, the lining epithelium of the mantle; e, the lens; jf, the ligament
supporting the lens; g, the retina; h, the tapetum; k, the pigment;.m, the
retinal nerve; m, complementary nerve.

brates. That this distinctive character should thus
reappear in so distant a group is very interesting, and it
is also remarkable that Onchidium possesses two kinds of
eyes: some on the head, which are constructed on the
same type as those of other molluscs; while the peculiar
eyes just mentioned are scattered over the back, and
their nerves arise, not from the cephalic, but from the
visceral ganglion. Moreover, they differ in number,
not only in the different species, some having one hun-
dred, some as few as twelve, and others none at all,
but even in different individuals of the same species.
Indeed, they are continually growing and being re-
absorbed. But while thus resembling a simple verte-
brate eye, the dorsal eyes of Onchidium have a totally

* “Ueber Schnecken Augen am Wirbelthier typus,” Arch. fiir Mic.
Anat., 1877.

144 ONCHIDIUM. .

different development, arising, except the nerve, entirely
from the integument; on the contrary, in the vertebrate
eye, while the cornea and lens are formed from the
skin, the retina is an outgrowth from the brain.

Semper does not suppose that the Onchidia perceive
any actual image with their dorsal eyes, and thinks that
they are merely able to distinguish differences in the
amount of light.

They are shore-living molluscs, and are preyed on
by small fishes belonging to the genus Perophthalmus,
which has the curious habit of leaving the water and
walking about on the sand in search of food. The
back of the Onchidium contains a number of glands,
each opening by a minute pore; and Semper suggests
that, when warned by the shadow of the fish, the little
slugs eject a shower of spray, drive off their enemy,
and save themselves. This is not quite so far-fetched
as might at first sight appear, for we know that there
are many other animals, the sepia, many ants, the
bombardier and other beetles, etc., which defend them-
selves in a similar manner.

It seems difficult to understand why the Onchidia
should be endowed with so many eyes. The irrelative
repetition of organs meets us, however, continually in
the lower animals. Moreover, in the present case
Semper has thrown out a plausible suggestion. The
organs of touch (see ante, p. 14) curiously resemble
eyes in structure, and a very slight change might
make them capable of perceiving light. It is possible,
then, that some of them may undergo a change of
function, and that this may throw some light on the
variability in number.

In the Chitonidee, where dorsal eyes have recently

SENSE-ORGANS OF CHITON. 145

been discovered by Moseley,* they are even more
numerous. Chiton itself, indeed, has none; but in
Schizochiton there are 300, and in Corephium more

Fig. 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. 4a,
Conical termination of sense-organ ; b, b’/, ends of nerve; c, nerve; jf, calcareous
cornea ; g, lens; h. iris; k, pigmented capsule of eye; m, body of sense-organ cut
across; ”, nerve of eye; p, nerve of sense-organ; 7, rods of retina.

than ten thousand. As in Onchidium, they probably

arose as modifications of the organs of touch, and are

supplied by the same nerves. They possess (1) a

cornea, (2) a perfectly transparent and strongly biconvex

lens, and (8) the retina, which presents a layer of short
but well-defined rods. It is interesting that they point
towards the light, and not, as in Onchidium, away
from it.

* “On the Presence of Eyes in Shells of certain Chitonide,”’

Quarterly Journal of Microscopal Science, 1885. 7

CHAPTER VIZ.
THE ORGANS OF VISION IN INSECTS AND CRUSTACEA.

I now pass on to the eyes of insects. In most species
of this group there are two distinct kinds: the large
compound eyes, which are situated one on each side
of the head; and the ocelli, or small eyes, of which -
there are generally three, arranged in a triangle,
between the other two.

Speaking roughly, the ocelli of insects may be said
to see as our eyes do; that is to say, the lens throws
on the retina an image, which is perceived by the fine
terminations of the optic nerve. One type of such an
eye in a young water-beetle (Dytiscus) is shown in
Fig. 84,p. 131. This illustrates the mode of develop-
ment of an ocellus, which has been already referred to
(ante, p. 181). —

The structure of fully formed ocelli is shown by
Fig. 99. In details, indeed, they present many dif-
ferences, and it is remarkable that in some species this
is the case even with those of the same individual; for
instance, in those of one of our large spiders, Epeira
diadema (Fig. 99).

In this case the eye B would receive more light,
and the image, therefore, would be brighter; but, on

i ox

OCELLI. 147

the other hand, the image would be pictured in greater
detail by the eye A.

a5 = HIN

Fig. 99.—Long seciion through the front (A) and hinder (B) dorsal eyes of Zpeira
diadema (after Grenacher). A, Anterior eye; RB, posterior eye; Hp, hypoderm ;
Ct, cuticle; ct, boundary membrane; K, nuclei of the cells of the retina; MV, mus-
cular fibres; MM, M', cross sections of ditto; St, rods; Pg, P', pigment cells;
L, lens; Gk*, vitreous body; Kt, crystalline cones; Rt, retina; Nop, optic nerve.

Speaking generally, an ocellus may be regarded as
consisting of—

1. A lens, forming part of the general body covering.

2. A layer of transparent cells.

3. A retina, or second layer of deeper lying cells,

-each of which bears a rod in front, while their inner
ends pass into the filaments of the optic nerve. |

4. The pigment.

From the convexity of the lens it would have a
short focus, and the comparatively small number of
rods would give but a very imperfect image, except
of very near objects.

But though these eyes agree so far with ours, there
is an essential difference between them. It will be at

148 COMPOUND EYES.

once seen that the pigment is differently placed, being
in front of the rods, while in the vertebrate eye it is
behind them. Again, the position of the rods them-
selves is reversed in the two cases.

Passing on to the compound eye, Fig. 100 gives a
section of the eye of a cockchafer (Melolontha), after
Strauss-Diirckheim. The separate facets of such an

Fig. 100.—Section through the eye of a cockchafer (Melolontha) ; after Strauss-
Diirckheim.
eye act themselves as lenses, and give a very perfect
image. |
As regards the number of facets, Leeuwenhoek caleu-
lated that there were 3180 facets in the compound eye
of a beetle which, however, he does not name. In the
house-fly (Musca) there are about 4,000; in the gadfly
(Cistrus), 7,000; in the goat moth (Cossus), 11,000;
in the death’s-head moth (Sphinz atropos), 12,000 ;
in a butterfly (Papilio), 17,000; in a dragon-fly
(Aischna), 20,000; in a small beetle (Mordella), as
many as 29,000.

STRUCTURE OF THE COMPOUND EYE. 149

The size of the facets seems to bear some relation to
the size of the insect, but even in the smallest species
none have been observed Jess than g,9 of an inch in
diameter. Butterflies, which fly in the day, have the
facets smaller than those of moths, which are generally
evening insects.

The facets are in most cases similar, six-sided, and

Fig. 101.—Section through the eye of a fly (after Hickson). 6.m, Basilar membrane ;
c, cuticle; c.op, epioptic ganglion; m.c., nuclei; m.c.s., nerve-cell sheath; .f,
decussating nerve-fibres ; op, optic ganglion ; pe., pseudocone; pg, pigment cells;
p.op, perioptic ganglion; 7, retinula; Rh., rhabdom; 7, trachea; ¢.a., terminal
anastomosis; Jt, trachea; tz, tracheal vesicle.

very regular. In locusts, however, they vary a good

deal both in form and size. In some flies (Diptera)

and dragon-flies (Libellulide) those in the upper part
of the eye are larger than the lower ones, and the
junction of the two often forms a well-marked, curved

line.

150 CORNEA—CRYSTALLINE CONES.

The wonderful complexity is well shown in the pre-
ceding figure, which represents a section through the
eye of a fly, after Hickson.*

In illustration of the finer structure, I may take the
eye of the bee (Apis) (Fig. 102), as described and
figured by Grenacher in his beautiful
work.f Fig. 102, the general accuracy
of which has been confirmed recently
by Dr. Hickson, represents two of the
elements of the faceted eye.

The structure of the eyes varies
considerably in different groups. They
may be said to consist of the following
principal parts :—

1. The cornea (Lf, Fig. 102).

2. The crystalline cones (Kk), of
which there is one immediately behind
each facet. The development of the
crystalline cone has been carefully
Fig. 102—Two sepa studied by Claparede. It consists of

rate elements of the

faceted eye of a bee from four to sixteen original, but com-
(after Grenacher).

Lf. Cornea; m, mu- pletely combined segments, secreted

cleus of Semper ;

ne Sa eho J cells which lie immediately behind
cells. #1, retinula; each facet, but of which, when the eye
is completely developed, only the

nuclei, known as Semper’s nuclei (7), finally remain.
3. Next comes the retinula (r/), which stands in
more or less intimate connection with the pointed inner
end of the crystalline cone. It is generally composed

of seven, but sometimes of as few as four, or as many

* «The Eye and Optic Tract of Insects,” Quarterly Journal of

Microscopical Science, 1885. ;
+ “ Untersuchungen iiber das Sehorgan der Arthropoden.” 1879.

RETINULA—PIGMENT. ES!

as eight, originally separate, but closely combined cells.
They converge on the optic lobe, and form an outer
nucleated sheath, enclosing a strongly refractive,
generally quadrangular, rod (the rhabdom, fm), the
relation of which to the filaments of the optic nerve
is not yet well understood.

4. The pigment (Pq).

Between each separate eyelet (ommateum, or omma-
tidium, as it is termed by Hickson), is—at least, in
some insects—a long, tubular, thin-walled trachea.
These are difficult to see in prepared specimens, but
have been mentioned by several observers. They were
first, 1 think, figured by Leydig,* and more recently
by Hickson.

Finally, the eye is bounded by a basilar membrane,
which is perforated by two sets of apertures, a series of
larger ones for the passage of the tracheal vessels, and
of smailer ones for the nerve-fibrils.

The erystalline cone is not, however, always present,
and Grenacher divides the compound eyes of insects
into three types: acone eyes, in which the crystalline
cone is not present, but is represented throughout life
by distinct cells ; pseudocone eyes, in which there is a
special conical and transparent medium ; and, lastly,
eucone eyes, with true crystalline cones.” f

* “Zum feineren Bau der Insekten,”’ Miiller’s Arch. fiir Anat. u.
Phys., 1855.

+ Acone eyes occur in Nematocera (gnats), Hemiptera (bugs), For-
ficula (earwigs), and those Coleoptera (beetles), which have less than
five tarsal joints. Pseudocone eyes occur in the true flies (Muscidz).
Eucone eyes prevail among other insects: Lepidoptera, Hymenoptera,
Neuroptera, Orthoptera, Cicadide, the Coleoptera with five tarsal
segments, and among Diptera the single genus Corethra, which, more-
over, is remarkable as possessing compound eyes, even in the larva
and pupa,

152 DIFFERENT FORMS OF EYES.

The last form differs principally from the two first
in that the elements which constitute the crystalline
cone and the retinula have become completely coalesced
and solidified. The differences are, no doubt, im-
portant, but I need not enter into them at length here.

Even the eucone eyes differ considerably, as may be
seen from the following figures, representing (Fig. 103)
an eyelet from the eye of a cockroach (Periplaneta), and

(Fig. 104) one from that of a cockchafer (Melolontha),

both taken from Grenacher.

Fig. 103.—Eyelet of cockroach (after Fig. 104.—Eyelet of cockchafer
Grenacher). / J, Cornea; kk, crys- (after Grenacher). Jf, Cor-
talline cone; pg’, pigment cell; 71, nea; kk, crystalline cone;
retinula; rm, rhabdom. pg. pg’, pigment cells; ri,

retinula ; 7l’, rhabdom.

With some few exceptions (Corethra, Libellula, etc.),
the larve of insects do not possess faceted eyes; indeed,
as a general rule their powers of vision are very limited,
or they are altogether blind. Most caterpillars have

STRUCTURE OF THE OPTIC LOBES. $53

on each side of the head five or six eye-spots, contain-
ing each a crystalline body, but, as we shall presently
see, they can probably do little more than distinguish
between light and darkness.

I do not propose to attempt to give here any detailed
account of the structure of the insect brain, but I must
say a few words on the subject. Between the brain
proper and the eye itself there are, in, for instance, the
blow-fly (Musca vomitoria), three distinct ganglionic
swellings, which Hickson, a copy of whose beautiful »
figure I have given (Fig. 101), terms the “ opticon”
(op), epiopticon (¢.op), and periopticon (p.op). It will
be seen that the nerve-fibrils do not pass in a direct
course, but actually decussate, or cross from one side to
the other, three times, once between each two ganglionic
swellings. ‘The optic lobes of the two sides are also con-
nected by a fibrous bundle. ‘he structure of the three
nervous swellings is also very complex. It consists of a
fine granular matrix, traversed by a meshwork of very
minute fibrille, and, at least in the periopticon, is col-
lected into a series of cylindrical masses. It is entirely
beyond our present range of knowledge to explain the
origin or purpose of these complex arrangements,
though we cannot doubt that they do serve important
functions. It is remarkable that these arrangements,
though apparently very constant in individual species
and genera, differ greatly in different groups of insects ;
for instance, Hickson asserts that in the water-scorpion
(Nepa), there is no decussation, and Carriére makes the
same statement as regards Libellula; but it seems
very extraordinary that this arrangement should be
present in some insect eyes, and absent in others
formed apparently on so nearly the same plan.

154 RELATIONS OF OCELLUS: AND EYE.

On THE RELATION OF THE EYE TO THE OCELLUS.

In considering the relation of the eye to the ocellus,
it is obvious that we cannot regard either as derived
from the other. They are, as Grenacher says, “ sisters,”
and derived from a common origin.

The ocellus consists of a single lens in front of a
larger or smaller number of visual rods. The com-
pound eye consists of a number of facets, each in front
of a single rod; which is produced by from four to
sixteen cells: in some cases each cell at first produces
a separate rod, and these then subsequently coalesce
more or less completely. Starting, then, from a simple
form of eye consisting of a lens and a nerve-fibre,
which would be capable of perceiving light, but would
give no picture of the external world, we should
arrive at the compound eye by bringing together a
number of such eye-spots, and increasing the number
of lenses, while the separate cells beneath each com-
bined to form a single cone and rod; while, on the
other hand, by increasing the size of the lens, and
multiplying the nervous elements behind it, we should
obtain the ocellus of an insect, or the typical eyes of
a vertebrate animal.

There is, indeed, no need to suppose that these two
eyes are derived from a common origin. We know
that, while very similar eyes occur in distant groups of
animals, on the other hand nearly allied species often
differ greatly in the structure of their eyes; that,
indeed, eyes of very different types often occur even in
the same animal, so that we have strong reasons for
assuming that they had an independent and separate
origin,

ES

OCELLI OF SPIDERS—MYRIAPODS. 155d

The spiders have simple ocelli only, the higher
Crustacea compound eyes only, while many of the
lower Crustacea and of the great class of the insects
possess both eyes and ocelli. It would seem probable,
therefore, that the ancestral stock must have possessed
both, though not perhaps in so perfect a form as that
which has now been attained, and that the spiders have
lest the compound eyes, while, on the contrary, in the
higher Crustacea the ocelli have disappeared.

Moreover, though the ocellus of a spider at first
sight closely resembles the eye of a Scolopendra, the
internal structure is, according to Grenacher, altogether
different. In the ocellus of a spider or an insect we
find, at a greater or less distance behind the lens, a
retina consisting of a receptive surlace, extended con-
centrically with that of the lens, and consisting of a
number of more or less rod-like perceptive elements so
arranged that the light falls on their ends.

On the contrary, in the eyes of Myriapods there is,
he says, either a single element behind the cornea, or
where there are many such elements, they are arranged
with their longer axes perpendicular to the direction
of light; so that any separate perception of the rays
of light coming from different points seems to be an
impossibility. In the eye of Lithobius, behind the
biconvex lens, he states that the cells linmg what I
may call the tube of each separate eye, terminate in

filaments, between the free ends of which is left a narrow

passage, down which the light must pass to reach the
end of the optic nerve. Such a structure is certainly
very remarkable, and seems entirely to preclude the
possibility of the formation of a true image. Altogether

the account given by Grenacher, both as to the mode

156 EYES OF CRUSTACEA.

of action of the eyes of the Myriapods and as to their
internal structure, differs entirely from that of Graber.

Fig. 105.—Leptodora hyalina.

THe Eves or CRUSTACEA.

The eyes of many Crustacea are highly developed.
In the higher families (thence named Podophthalmata,

q

STRUCTURE OF EYE Lo?

or stalk-eyed) they are situated on more or less
elongated pedestals. In some of the lower forms,
though less complex, they are very large, occupying,
as in the curious Leptodora (Fig. 105) of our deep
lakes, the whole front of the head; while in Coryceus

He 3 rn
5 cen 6
ilar 7 “agsexes oh
BAN 3 (aq J
Wf

Fig. 106.—Eye of Mysis (after Grenacher). n, Nuclei; Lf, facets; Kk, crystalline
cones; 7’, cells of the retinula; Rl, retinula; Rm, rhabdom; Cp, blood-vessels ;
NV, fibres of the optic nerve; WN’, NV‘, N'**, N'!"?, decussations of the fibres of the
optic nerve; G, G’, G', G'"', ganglia; 24 muscles for the movement of the
eye-stalk; Km', Km}, nuclei.

(Fig. 107) they extend to more than one-half of the

whole length of the body.

The higher Crustacea possess no ocelli. In the
lower species, on the contrary, a central ocellus is often
present, especially in the young state.

158 MYSIS—CORYCHZUS—COPILIA.

In illustration of the compound eyes of Crustacea, I
give a figure of an eye of Mysis (Fig. 106).

In the higher Crustacea the nervous elements of
the eye are, moreover, very complex. There are no
less than four optic ganglia (Fig. 106), and there is
a chiasma, or decussation of fibres (N14, VN", N44, N41"),
between each. |

The eyes of lobsters and of crabs offer a curious
difference. In the former, the crystalline cones are
very long, and the retinule comparatively short ; while
in the crabs, on the contrary, the crystalline cone is
short, and the retinule long.

The eye of Coryceus (Fig. 107) is very- interesting.
It is extremely large in proportion to the size of the

Fig. 107.—Coryceus (after Leuckart). a, b, The eye.

animal, extending from the front of the head to the
beginning of the abdomen. ‘The perceptive part of
the eye (5) is, therefore, far removed from the lens (a).
The eye of Coryczeus appears to represent, in fact, a
single element of a compound eye.

The eye of Copilia is also very remarkable, the
retinula being, at about the end of the first third of its
length, bent at a right angle. Here also the eye is
about one-third as long as the body.

The ocelli of Crustacea have not been much studied
with reference to their microscopic structure. ‘Those

i —- ee lle

7, = --—

CALANELLA—LIMULUS. 159

of Calanella are very remarkable, and, indeed, but for
their position and the presence of pigment, would
hardly be recognized as eyes. ‘hey are three in
number,and together form an X-shaped body (Fig. 108),
supplied by a large nerve (NV.op.), and consisting of
three groups of large nerve-cells, embedded in pig-
ment. ‘There are eight in each of the two side groups,
and ten in the central. In form they are pear-shaped,
with the narrow end turned towards the nerve. The
organ contains no lens nor rods.

Fig. 108.—Eyes of Calanella Mediterranea (after Gerstarker) Pg., pigment cells;
N.fr., frontal nerves; op., nervus opticus. The numpfers show the numbcrs
of the cells.

The eyes of the king crab (Limulus) have. been

_described by Grenacher and by Lankester and Bourne.*

The two lateral eyes form a polished, kidney-shaped
protuberance on each side of the great shield. ‘the
outer side is smooth, but on the inner surface it is
produced into a number of conical processes (Fig. 109),

* <QOn the Eyes of Scorpio and Limulus,” Quarterly Journal of
Microscopical Science, 1883.

9

160 LIMULUS. |

each of which forms a special lens. Underneath each
of these secondary lenses is a group of large, elongated
pigmented cells, arranged round a central space, and
touching the lens with their outer ends, while the

H

HH

Tal

Fig. 109.—Diagram of a vertical section through a portion of the lateral eye of Limulus
polyphemus, showing some of the conical lenses, and corresponding retinule (after
Lankester and Bourne). a, Cuticle; 00, cuticular lens; cc, hypoderm; Rn,
retinula; m, nerves.

inner ones are continued into the optic nerve. These

nerve-end cells form the “retinula,” while their sides,

which face one another, are thickened, and coalesce
into a rod, the rhabdom, which is hollow at the end
nearest the lens, but solid towards the nerve. The
central eye is very different. It possesses a single
lens, like that of an ordinary ocellus, underneath
which is a layer of cells not differing much in appear-
ance from those of the hypoderm, and below which
again is another layer of large nerve-cells, which, how-
eyer, are so irregular as to suggest the idea that the
central eye of the king crab may have partially lost its
function. The king crab, then, so remarkable in other
ways, is also very interesting in reference to the peculiar

i m
iii
I wi
Hil
AAA
il
i |
A

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SCORPIONS—LIGHT-ORGANS OF EUPHAUSIA. 161

structure of its eyes. These can hardly be regarded
as homologous with the compound eyes of insects and
Crustacea, but appear to have originated independently.
They have, indeed, hardly anything in common, except
that of being compound eyes.

Lastly, I may allude to the eyes of scorpions,
which, though very different from those of Limulus
in appearance, in Lankester’s opinion approach them
more nearly in essential constitution than any other
known eyes.

Before quitting this part of my subject, 1 must
mention the curious eye-like organs of Kuphausia.

Kuphausia (Fig. 110)—a shrimp-like crustacean, be-

Fig. 110.— Zuphausia pellucida (after Sars). U.0,, Luminous organ.

longing to the same group as Mysis—and some of its
allies, are remarkable for possessing at the base of
some of the thoracic legs, and on the four anterior
abdominal segments, luminous eye-like organs. They
form small bulbs, each containing a vitreous body, some
pigment, a lens, and a fan-shaped bundle of delicate
fibres, and are very conspicuous from their beautiful
red color and glistening lustre.

162 LIGHT-ORGANS OF EUPHAUSIA.

Claus * regards them as true accessory eyes. Sars,f
on the contrary, considers that they have no power of
sight, but are highly differentiated luminous organs.
He admits that they present a deceptive resemblance
to true eves, but has convinced himself by observations
of the living animal that they have no power of
vision.

The fibrous fascicle (Fig. 111, f) he finds to be the
chief light-producing part,f and the lens-like body in
front serves, as he supposes, for a condenser, producing
a bright flash of light, the direction of which the
animal, by means of its muscles, is able to control.
The anterior pair (Fig. 112, lo), which differ some-
what in structure from the rest, are situated on the

Fig. 111.—Luminous organ of
Euphausia (after Sars).

Fibres ; ¢, lens. | Fig. 112.—Eye-stalk of Euphausia (after

Sars). lo, Luminous organ; a, lower
eye.

eye-stalks, and appear to serve as “ bull’s-eyes” to

the true organs of vision. Sars considers that the
luminous organs do not serve as eyes, on the grounds

* “Ueber einige Schizopoden und niedere Malacostraceen,” Zeét.
fiir Wiss. Zool., 1863.

+ “On the Schizopoda,” “Challenger Reports,” vol. xiii.

{ Valentine and Cunningham, in a memoir just published
(Quarterly Journal of Microscopical Science, vol. xxviii.) deny this, and
attribute it to the inner surface of the reflector.

F
|

MODE OF VISION BY COMPOUND EYES. 163

that the nerve which supplies them is but small; that
the structure is not really analogous to that of a true
eye, and that the position would be very unsuitable,
one of them being actually situated on the stalk of
the compound eye.

The question does not, however, seem to be by any
means clearly solved, and it must, I think, be admitted
that, with the exception of the anterior pair, if the
position does not seem suitable for true eyes, neither
is it that which one would expect in light-vrgans,

On THE MopeE oF VISION BY MEANS OF
COMPOUND EYES.

Johannes Miller, in his great work on the Physiology
of Vision,* was the first to give an intelligible explana-
tion of the manner in which insects see with their com-
pound eyes. According to his view (see Fig. 75),
those rays of light only which pass directly through
the crystalline cones, or are reflected from their sides,
can reach the corresponding nerve-fibre. The others
fall on and are absorbed by the pigment which separates
the different facets. Hence each cone receives light
only from avery small portion of the field of vision,
and the rays so received are collected into one spot
of ight. The larger and more convex, therefore, is the
eye, the wider will be its field of vision; while the
smaller and more numerous are the facets, the more
distinct will the vision be. In fact, the picture per-
ceived by the insect will be a mosaic, in which the
number of points will correspond with the number of

facets.
* “Zur vergleichenden Physiologie des Gesichtsinnes.”

164 MULLER’S THEORY OF MOSAIC VISION.

This theory was at first received with much favour.
In 1852, however, Gottsche * attacked Miiller’s view,
pointing out that each separate cornea of a compound
eye can, and in fact does, give a separate and distinct
image. This had, indeed, long previously been ob-
served by Leeuwenhoek, who said, “When I removed
the tunica cornea a little from the focus of the micro-
scope, and placed a lighted candle at a short distance,
so that the light of it must pass throngh the tunica
cornea, | then saw through it the flame of the candle
inverted, and not a single one, but some hundreds of
flames appeared to me, and these so distinctly (though
wonderfully minute) that I could discern the motion of
trembling in each of them.” t ; |

Of this, indeed, it is easy to satisfy one’s self. It is
only necessary to look at a candle through the cornea
of an insect, and then slightly draw back the micro-
scope, when a thousand small images of the candle,
each formed by one of the lenses, will be plainly seen.
If, then, in such cases there was a retina placed at the
proper distance, a true image would be formed, as on
the retina in our own eyes. This paper of Gottsche’s
threw great doubt on Milier’s explanation, which,
indeed, was, in Dors’s words, “ abandonnée par tout le
monde.” t

It is one thing, however, to see that the lenses throw
distinst pictures, but quite another to understand how
such pictures could be received on the retina, or com-
bined into one distinct image.

* “Beit. zur Anat. und Phys. der Fliegen und Krebse,” Miiller’s
Arch., 1852.

t+ A. Van Leeuwenhoek, “ Select Works,” translated by S. Hoole.

t “De la vision chez les Arthropodes,” Ar. des Sct. Phys. et Nat.
Geneva: 1861.

IMAGES THROWN BY THE CORNEA. 165

It must, moreover, be remembered that in our eyes
the whole field of vision is reversed, so that different
objects remain in the same relative position. In the
ease of insects, however, it would be the image thrown
by each facet which would be reversed, and hence the
general effect would be altogether false.

We must not attach too much importance to the
mere presence of an image. Any lens-like object, even
a globule of fat, will give one. Moreover, as Miller
and Helmholtz have shown, the lenses of the cornea
would be an advantage on the theory of mosaic vision,
by assisting to condense the rays of light on the
termination of the nerve. 7

Gottsche’s observation was made on the eye of the
blow-fly (Musca vomitoria), and, as a matter of fact, the
fly is one of those insects which do not possess a true
crystalline cone. It is, therefore, probable that. the
image which he saw was that of the cornea. Moreover,
as is shown by his figure, which I give below (Fig. 113),
he states* that the image was formed at x, while the
retina is far away at y. He suggested, indeed, that
the so-called optic ganglion really corresponds with
the retina of our own eye; but this would not remove

* His words are—“ An der hintern Flache der Crystallkorper im
Fliegenauge kehrt sich sicher das Bild um, weil das Bild dem object
in der Lage gleich ist, und da das Mikroskop das Object einmal
umkehit, so muss hier eine doppelte Umkehrung stattfinden, einmal
durch das Mikroskop und vorher durch den parabolischen Crystall-
korper. Entsteht nun bei x (Fig. 113) ein umgekehrtes Bild, so ist
die Frage, wird das ganze Bild von x durch den Stiel zur Retina
und zur Perception bei y hingeleitet oder wirkt dieser diinne Stiel
gleichsam wie ein Diaphragma und giebt er nur einen ‘Theil des
Bildes bei x nach y ” (Gottsche, “ Beit. zur Anat. und Phys. des Auges
der Krebse und Fliegen,” Arch. fiir Anat. Phys. und Wiss. Medicin.,
1852).

166

MOSAIC VISION.

the difficulty, because, if any definite picture is to be
formed, the sensitive rods, cones, or other structures

Fig. 113.—One of the
elements of the eye
at (ca “aly ater
Gottsche). kk, Crys-
talline cone; x, posi-
tion of the image;
s, rod; sc, sheath;
scm, outer sheath;
7, retina ; y, seat of
vision.

must lie in the plane of the image,
and this is not, in fact, the case.

Dor suggested that the crystalline
cones are nervous structures, and cor-
respond to the ruds of the vertebrate
eye (Fig. 79). He admits, however,
that, as a matter of fact, the image is
not formed at the anterior surface of
the crystalline cones.*

And yet in his final summary,
having shown that the image is formed,
not at the anterior surface, but deep
down in the erystalline cones, he
expresses quite a different view,
compares the crystalline cone to
the vitreous body, and considers that
the true retina is to be found in an
envelope which surrounds the cone.

Plateau f regards the mosaic theory
of Muller as definitively abandoned,
but rather seems to have had in his

mind that of Gottsche. At least, he states that, accord-
ing to Miiller, the mosaic is formed by a number of
partial images, each occupying the base of one of the
elements composing the compound eye. ‘his, how-
ever, is not Miiller’s theory.

* “Ta cornée avec sa convexité postérieure correspond & la cornée
et au cristallin des vertébrés, le corps cristallin (avec le soi-disant
corps vitré) et la fibre nerveuse qui s’y attache a la couche des
batonnets, enfin le ganglion optique a celles des couches de la rétine, qui
sont composées des granulations, des cellules, et des fibres nerveuses.”

+ “Rech. Exp. sur la Vision des Arthropodes.” Bruxelles: 1887.

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_ ee ee ee ee

OBJECTIONS TO OTHER THEORIES. 167

On the other hand, Boll,* Exner,f and Grenacher
seem to me to have proved that the compound eyes of
insects cannot act as ours do; that the theory which
assumes that each facet acts as a separate eye and
projects an image on a retina, 1s physically untenable.

In the first place, there are cases—for instance,
Forficula, Dytiscus, and Stratiomys among insects ;
Ligia and many others among Crustacea—where tlie
corneee are not sufficiently arched to give any distinct
image. But even where an image is thrown by the
cornea, it would be destroyed by the crystalline cone.

In certain Crustacea the crystalline cones are
elongated and curved; this, which Oscar Schmidt ¢
regarded as fatal to Miller’s theory, is, on the con-
trary, as Exner has pointed out, quite compatible with
it, but, on the contrary, cannot be reconciled with the
theory of an image.

There are few beetles in which the cornea give
better images than in the firefly (Lampyris splendidula).
On the other hand, the crystalline cones entirely
destroy these images. If the eye is looked at through
a microscope, and the crystalline cones are left 7n sztu,
the field of view appears perfectly black, with a bright
spot of light at the end of each cone. No trace of an
image ‘can be any longer perceived. In fact, the
images seen by i Peonhanke aud Goitsche are thrown
by the cornea only. ,

In most cases, then, it would appear that the image
formed by the cornea is destroyed by the crystalline

* “Beit. zur Phys. Optik,” Arch. fiir Anat. Phys. und Wiss. Medicin.,
1871.

¢ “ Ueber das Sehen von Bewegungen und der Theorie des
zusammengesetzten Auges,” Sitz. K. Akad. d. Wiss. Wien., 1875.

t Ibid., 1876.

168 POSITION OF THE IMAGE.

cone. This does not, indeed, always occur; but even in
such cases the image does not coincide with the posterior
end of the cone. Grenacher repeated the experiment
of Gottsche with moths. Here the crystalline cones
are firm, and are attached to the cornea. Thus he was
able to remove the soft parts, and to look through the
cones and the cornea. When the microscope was
focussed at the inner end of the cone, a spot of light
was visible, but no image. As the object-glass was
moved forward, the image gradually came into view,
and then disappeared again. Here, then, the image is
formed in the interior of the cone itself. Exner had
endeavoured to make this experiment with the eye of
Hydrophilus (the great black water-keetle), but the
crystalline cones always came away from the cornea.
He, however, calculated the focal length, refraction,
etc., of the cornea, and concluded that, even if, in spite
of the crystalline cone, an image could be formed, it
would fall much behind the retinula. In these cases,
then, an image is out of the question. Moreover, as
the cone tapers to a point, there would, in fact, be no
room for an image, which must be received on an
appropriate surface. In many insect eyes, indeed, as in
those of the cockchafer (Fig. 100), the crystalline cone
is drawn out into a thread, which expands again before
reaching the retinula. Such an arrangement seems
fatal to any idea of an image.

Moreover, for definite vision by the formation of an
image, it is necessary that the eye should possess some
power of accommodation for different distances. It is
obvious, from Fig. 76, that no distinct vision would
be given unless the receptive surface follows the
line a' b' c’. But the position of this surface will

ABSENCE OF POWER OF ACCOMMODATION. 169

depend upon the distance of a 6c from the lens. As
a matter of fact, Leydig * and Leuckart f thought they
had discovered, between the cornea and the crystalline
cones, certain muscular fibres which might regulate
the distance between the two, and thus effect this
object. Subsequent observers, however, have failed to
detect these fibres.

Again, it will be seen, from a glance at Fig. 76,
that in an eye constituted like ours, on the principle
of a camera obscura, the retina must follow a regular
curve. If it is brought at all too far forward, or forced
the lea-t too far back, the image is at once blurred.
Hence, in our own case the frequent need for spectacles,
and hence it would seem that a conical retina is a

physical impossibility.

Plateau, indeed, adopts{ a suggestion made by
Grenacher that the absence of any means of adaptation
may be rendered unnecessary by the length of the
cones, the rays coming from distant objects acting on
the anterior end, those from nearer ones at a greater or
less depth. This, I confess, seems to me inadmissible.
In the first place, the light must surely act immedi-
ately it impinges on the organ of perception ; and, in
the second, the cones are, as a general rule, abso-
lutely transparent—the light passes unimpeded through
them.

_ Again, if insects sce with their compound eyes as we
do with ours, they must, of course, possess a retina.
No such structure, however, has been as yet shown to

* “Zum feineren Bau der Arthropoden,” Miiller’s Arch. fiir Anat.
und Phys., 1855.

+ “Carcinologisches,” Wiegmann’s Arch., 1858.

¢ “Rech. Exp. sur la vision chez les Arthropodes,” 1887.

170 ABSENCE OF RETINA.

exist. Waener,* indeed, observed that in some eases
the optic nerve embraces the end of the cone, and he
supposed that it thus forms a sort of retina, for which,
however, its form is little suited. |

I ought also to mention that Max Schultze f con-
sidered that he had, in some few cases—for instance,
in Syrphus—been able to observe that the termina-
tion of the nerve does divide into a number of fibres.
Patten,f more recently, has also maintained the
existence of numerous nerye-fibrils, which, however,
subsequent observers—for instance, Kingsley § and
Beddard |—have been unable to discover. Even, how-
ever, if we admit the perfect correctness of Schultze’s
observation, these cases are exceptional, and the fibres
so few that they can hardly, I think, affect the general
conclusion. ‘To give anything like a distinct vision, a
very large number would be required.

A last objection is the extreme difficulty which
would exist of combining so many different images
into one idea, though it must be admitted that at first
sight this difficulty (though to a minor degree) exists
even in the case of simple eyes, the number of which

varies considerably. Spiders have six to eight; some —

aquatic larvee twelve; while the Oniscoidee (wood-lice),
assuming that their eyes are aggregates of simple eyes,
as Miller supposed, have as many as twenty to forty.

* Kinige Bemerk. iiber den Bau der zus. Augen,” Arch. fiir Nat.,
1835.

+ ‘“ Unt. iiber die zus. Augen der Krebse und Insecten,” 1868.

{ “Eyes of Molluscs and Arthropods,’ Mitth. Zool. St. Neapel, 1886.

§ “On the Divisions of the Compound Eye,” Journal of Morphology,
1887.

| “On the Structure of the Eye in Cymothoide,” Trans. Roy. Soe.
Edin., 1887.

ee eee) ee ee. a ee

SUMMARY. 171

These, however, take in different parts of the field of
vision.

The principal reasons, then, which seem to favour
Miiller’s theory of mosaic vision are as fullows :—
(1) in certain cases—for instance, in Hyperia—there
are no lenses, and consequently there can be no image ;
(2) the image would generally be destroyed by the
crystalline cone; (3) in some cases it would seem that
the image would be formed completely behind the eye,
while in others, again, it would be too near the cornea;
(4) a pointed retina seems incompatible with a clear
image; (5) any true projection of an image would in
certain species be precluded by the presence of im-
penetrable pigment, which only leaves a minute central
passage for the light-rays; (6) even the clearest
image would be useless, from the absence of a suit-
able receptive surface, since both the small number
and mode of combination of the elements composing
that surface seem to preclude it from receiving more
than a single impression ; (7) no system of accommoda-
tion has yet been discovered. Finally, (8) a combina-
tion of many thousand relatively complete eyes seems
quite useless and incomprehensible.

ON THE PowER OF VISION IN INSECTS, ETC.

As regards the practical vision of insects, our know-
ledge is still very imperfect. No one, indeed, who has
observed them can doubt that in some the sight is
highly developed. It is impossible, for instance, to
watch a dragon-fly hawking over a pond,—to see the —
rapidity and accuracy of its movements, and doubt
that it can see well.

172 ON THE POWER OF VISION IN INSECTS.

On the other hand, Claparéde asserts that at a
distance of twenty feet a hive bee would be unable to
see any object which was less than eight or nine inches —
in diameter, and even at a distance of a foot he says
that each facet would correspond to an inch and a third.

To determine how far a faceted eye could see, he
tukes the breadth of a facet, the radius of the eye-
sphere, and the smallest angle of vision, and the dis-
tance in centimetres at which the facet would cover
a centimetre, and finds for the bee, for instance, 6°7
centimetres.

He then proceeds to inquire at what distance from
the faceted eye the image is as clear as in the human
eye, and he thinks this would be about a millimetre,
from which it would rapidly diminish, being only 75 at
a centimetre, and at a metre no distant vision being
possible; so that at a very little distance such eyes
would be as good as useless.

“In the human eye, for example, the distance
between the centres of two adjacent cones is only
yoyo Mm., but in Musca the distance between adjacent
ommatidia is 735mm. In fact, the picture, as received
by the nerve-end cells of the Vertebrate eye, is much
more complete in itself than it can possibly be in any
Arthropod eye, and consequently the latter possesses
a much more elaborate and complete translating appa-
ratus in its retina than the former possesses.” *

Claparéde arrives at this conclusion by taking
the average curvature of the whole eye, as b.ing true
for each part. ‘his, however, is not the case, and
in the central region of the eye the adjacent facets

* §. J. Hickson, “The Eye and Optic Tract of Insects,” Quarterly
Journal of Microscopical Science, vol. xxv., new series, 1885, p. 242.

EXPERIMENTS ON VISION OF INSECTS. Via

make but a small angle with one another. Lowne has
ealeulated that wasps, humble bees, dragon-flies, etc ,
would, at a distance of twenty feet, be able to distinguish
objects from half an inch to an inch in diameter. ‘Thus
a dragon-fly would see an object twenty feet from its
eye in the same detail that a man would perceive it at
a distance of a hundred and sixty feet.

Moreover, when Claparede * observes that bees will
return from a considerable distance straight to the door
of their nest, and that, under Miller’s theory, the door
would at such a distance be absvlutely invisible, he
forgets that the bee first probably guides itself by the

known position of the door in relation to some tree or

other large object, then with reference to the hive
itself, and that it is quite unnecessary to assume that
the door is actually seen from a distance.

With reference to the power which insects possess
of determining form, Plateau t has recently made some
ingenious experiments. Suppose a room into which
the hght enters by two equal and similar orifices, and
suppose an insect set free at the back of the room, it
will at once fly to the light, but the two openings
being alike it will go indifferently to either one or the
other. That such is the case Plateau’s experiments
clearly show, and, moreover, prove that a comparatively
small increase in the amount of hght will attract
the insect to one orifice in preference to the other. It
occurred then to Plateau to utilize this by varying the
form of the opening, so that the light admitted being

* “Zur Morph. der zus. Augen bei den Arthropoden,”’ Zeit. fiir
Wiss. Zool., 1860.

+ Bull. de lTAcad. Roy. de Belgique, t. x., 1885; Comptes Rendus de

la Soc. Ent. de Belg., 1887; “ Rech. Exp. sur la Vision chez les
Arthropodes,” 1887.

174 EXPERIMENTS ON VISION OF INSECTS.

equal, the opening on the one side should leave a clear
passage, while that on the other should be divided by
bars large enough to be easily visible, and sufficiently —
close to prevent the insect from passing.

His experiments were conducted in a room five
metres square, lighted by two similar windows looking
to the west. It was on the first floor, and looked out
on to fields. Moreover, he had the glass of the windows
slightly ground, so that, while the light penetrated,
nothing outside could be seen. He then covered up
the windows, leaving only two orifices, one of which
was simple and square, while the other was divided
by cross-bars. ‘To secure equality of light, the latter
was left somewhat larger than the other, and the
equivalence of the two was determined by a Rumford’s
photometer. The insects were set free on a table at
the back of the room, exactly between the two open-
ings, and at a distance of four metrés. He states that
a very slight difference in the intensity of the light
determined the flight of the insect to either one or the
other opening; while, if the amount of light was as
nearly as possible equal, they flew as often to the one
as to the other.

Omitting the cases when the light was not equal, the
numbers were as follows :—

Clear Trellised

opening. opening.
Musca vomitoria (the bluebotitle) ... a a> Oe
On the other hand, they were—for

Eristalis tenax (the bee fly) as SE
Vanessa urtice (tortoiseshell butterfly)

In fact, then, the msects seem to have gone more

EXPERIMENTS ON VISION OF INSECTS. LTS

often to the trellised opening. M. P:ateau concludes
that insects do not distinguish differences of form, or
can only do so very badly (“Ils ne distinguent pas la
forme des objects ou la distingnent fort mal”’).

I confess, however, that these experiments, ingenious
as they are, do not seem to me to justify the conclu-
sions which M. Plateau has deduced from them.
Unless the insects had some means of measuring
distance (of which we have no clear evidence), they
could not tell that even the smaller orifice might not
be quite large enough to afford them a free passage.
The bars, moreover, would probably appear to them
somewhat blurred. Again, they could not possibly
tell that the bars really crossed the orifice, and if they
were situated an inch or two further off they would
constitute no barrier.

I have tried some experiments, not yet enough to be
— conclusive, but which lead me to a different conclusion
from that of M. Plateau. I trained wasps to come to
a drop of honey placed on paper, and, when the insects
bad learned their lesson, changed the form of the paper,
as i had previously changed the color. It certainly
seemed to me that the insect recognized the chance.
M. Forel has also tried similar experiments, and with
the same result.

We know, however, as yet very little with reference |
to the actual power of vision possessed by insects.

On tHe FuNcTION OF OCELLI.

Another interesting question remains, What is the ©
function of the ocelli? Why do insects have two sorts
of eyes?

176 ON THE FUNCTION OF. OCELLI.

Johannes Miller considered that the power of vision
of ocelli “is probably confined to the perception of
very near objects. This may be inferred partly from
their existing principally in larve and apterous insects,
and partly from several observations which I have
made relative to the position of these simple eyes. In
the genus Empusa the head is so prolonged over the
middle inferior eye that, in the locomotion of the
animal, the nearest objects can only come within the
range. In the Locusta cornuta, also, the same eye lies
beneath the prolongation of the head. ... In the
Orthoptera generally, also, the simple eyes are, in
consequence of the depressed position of the head,
directed downwards towards the surface upon which
the insects are moving.”

From these facts, he considers himself justified in
concluding that the simple eyes of insects are intended
principally for myopic vision. The simple eyes bear
a similar relation to the compound eyes, as the palpi
to the antenne. Both the antenne and compound
eyes are absent in the larve of insects.” *

Lowne observes f that “the great convexity of the
lens in the ocellus of Hristalis must give it a very

short focus, and it is manifestly but ill adapted for.

the formation of a picture. The comparatively small
number of rods must further render the production
of anything like a perfect picture, even of very near
objects, useless for purposes of vision. I strongly
suspect that the function of the ocelli is the perception
of the intensity and the direction of light rather than
of vision in the ordinary acceptation of the term.”

* « Physiology of the Senses,” translated by Baly.
f “On the Modification of the Eyes of Insects,” Phil. Trans., 1878,

/

DIFFICULTY OF SUBJECT. ¥ti

Réaumur, Marcel de Serres, Dugés, and Forel also
have shown that in insects which possess both ocelli
and compound eyes, the ocelli may be covered over
without materially affecting the movements of the
animal ; while, on the contrary, if the compound eyes
are so treated, they behave just as if in the dark. For
instance, Forel varnished over the compound eyes of
some flies (Musca vomitortza and Lueilia cesar), and
found that, if placed on the grouud, they made no
attempt to rise; while, if thrown in the air, they flew
first in one direction and then in another, striking
against any object that came in their way, and being
apparently quite unable to guide themselves. They
flew repeatedly against a wall, falling to the ground,
and unable to alight against it, as they do so cleverly
when they have their eyes to guide them. Finally,
they ended by flying straight up into the air, and quite
out of sight. It seems, indeed, to be a very general
tule that insects of which the eyes are covered,
whether they are totally blinded, or whether the ocelli
are left uncovered, fly straight up into the air—a very
curious and significant fact of which I think no
satisfactory explanation has yet been given.

Plateau * regards the simple eyes, or ocelli, as rudi-
mentary organs of scarcely any use to the insect. Forel
also states, as the result of his observations, that wasps,
humble bees, ants, etc., find their way both in the air

and on the ground, almost equally well without as with

the aid of their ocelli.

I confess that I am not satisfied on this point. In
such experiments great care is necessary. M. Forel’s
interesting experiments with ants, whose compound eyes

* Bull. de? Acad. Roy. de Belgique, t. x., 1885.

178 EXPERIMENTS.

he had covered with opaque varnish, might almost, for
instance, be quoted to prove the same with reference
to the compound eyes. “Mes Camponotus aux yeux
vernis,” he says, “attaquaient et tuaient aussito6t une
Formica fusca mise au milieu d’eux, la saisissaient
- presque aussi adroitement que ceux qui avaient leurs
yeux. Ils déménageaient un tas de larves d’un coin
de leur récipient a l'autre avec autant de précision
qu’ avec leurs yeux.” *

On the other hand, Forel goes so far as to say that
if the compound eyes are covered with black varnish,
insects cannot even perceive light (“Cela prouve
qu’elles ne voyaient plus méme la lueur”). In fact,
the use of the ocelli seems a great enigma, at least
when the compound eyes are present.

We must remember that some other Articulata—
spiders, for instance—possess ocelli only, and they
certainly see, though not probably very well.

Plateau has made some ingenious observations, from
which it appears that spiders are very short-sighted,
and have little power of appreciating form. He found
they were easily deceived by artificial flies of most
inartistic construction; and he concludes that even
hunting spiders do not perceive their prey at a greater
distance than ten centimetres (about four inches), and
in most cases even less. Scorpions appeared scarcely
to see beyond their own pincers.

I have also made some experiments on this point
with spiders (Lycosa saccata). In this species, which is
very common, the female, after laying her eggs, collects
them into a ball, which she surrounds with a silken
envelope and carries about with her. I captured a

* Recueil Zool. Suisse, 1887.

SHORT SIGHT OF OCELLL 179

female, and, after taking the bag of eggs from her, put
her on a table. She ran about awhile, looking for her
egos, When she became still, I placed the ball of
eggs gently about two inches in front of her. She
evidently did not see it. I pushed it gradually towards
her, but she took no notice till it nearly touched her,
when she eagerly seized it.

IT then took it away a second time, and put it in the
middle of the table, which was two feet four inches
by one foot four, and had nothing else on it. The
spider wandered about, and sometimes passed close to
the bag of eggs, but took no notice of it. She
wandered about for an hour and fifty minutes before
she found it—apparently by accident. I then took it
away again, and put it down as before, when she
wandered about for an hour without finding it.

The same experiment was tried with other individuals,
and with the same results. It certainly appeared as if
they could not see more than half an inch before them
—in fact, scarcely further than the tips of their feet.

I may also mention that they did not appear to
recognize their own bags of eggs, but were equally
happy if they were interchanged.

On the other band, it must be remembered that the
sac is spun from the spinnerets, and the Lycosa had
perhaps actually never seen the bag of eggs. Hunting
spiders certainly appear to perceive their prey at a
distance of at least several inches.

Plateau has shown, in a recent memoir, that cater-
pillars, which possess ocelli, but no compound eyes,
are very short-sighted, not seeing above cne to two
centimetres.*

* “Rech. Exp. sur la Vision chez les Arthropodes.” Bull. de
"Acad. Roy. de Belgique, 1888. —

180 OCELLI OF CAVE-DWELLING SPIDERS.

Lebert has expressed the opinion* “that in spiders
some of their eight eyes—those which are most convex
and brightly coloured—serve to see during daylight ;
the others, flatter and colorless, during the dusk.”
Pavesi has observed f that in a cave-dwelling species
(Nesticus spelunearum), which belongs to a genus in
which the other species have eight eyes, the four
middle eyes are atrophied. Tuis suggests that they
serve specially in daylight.

Returning for a moment to the ocelli of true insects,
it seems almost incredible that such complex organs
should be rudimentary or useless. Muvreover, the
evidence afforded by the genus Eciton seems difficult
to reconcile with this theory. The species of this
genus are hunting ants, which move about in large
armies and attack almost all sorts of insects, whence
they are known as driver ants, or army ants. They
have no compound eyes, bnéi in the place of them
most species have a single large ocellus on each side
of the head, while others, on the contrary, are blind.
Now, while the former hunt in the open, and have all
the appearance of seeing fairly well, the latter con-
struct covered galleries, and seek their prey in hollow
trees and otner dark localities.

Insects with good sight generally have the crystalline
lenses narrow and long, which involves a great loss of
hight. The ocelli are specially developed in insects,
such as ants, bees, and wasps, which live partly in the
open light and partly in the dark recesses of nests.
Again, the night-flying moths all possess ocelli; while
they are entirely absent in butterflies, with, accord-

* “Die Spinnen der Schweiz.”
7 “Sopra una nuova Specie di Ragui.”

PROBABLE FUNCTION OF OCELLL 181

ing to Scudder, one exception, namely, the genus
Pamphila. )

On the whole, then, perhaps the most probable view
is that, as regards insects, the ocelli are useful in dark
places and for near vision.*

Whatever the special function of ocelli may be, it
seems clear that they must see in the same manner as
our eyes do—that is to say, the image must be reversed.
On the other hand, in the case of compound eyes, it
seems probable that the vision is direct, and the diffi-
culty of accounting for the existence in the same animal
of two such different kinds of eyes is certainly enhanced
by the fact that, as it would seem, the image given by
the medial eyes is reversed, while that of the lateral
ones is direct.

Forel, in his last memoir, inclines to this opinien,

CHAPTER VIII.
ON PROBLEMATICAL ORGANS OF SENSE.

In addition to the organs of which I have attempted
in the preceding chapters to give some idea, and to
those which from their structure we may suppose to
perform analogous functions, there are others of con-
siderable importance and complexity, which are evi-
dently organs of some sense, but “ use and purpose
of which are still unknown.

“Jt is almost impossible,” says Gegenbaur,* “to
say what is the physiological duty of a number of
organs, which are clearly sensory, and are connected
with the integument. These enlargements are generally
formed by ciliated regions to which a nerve passes,
and at which it often forms enlargements. It is
doubtful what part of the surrounding medium acts on
these organs, and we have to make a somewhat far-
fetched analogy to be able to regard them as olfactory
organs.”

Among the structures of which the use is still quite
uncertain are the muciferous canals of fishes. The
skin of fishes, indeed, contains a whole series of organs
of whose functions we know little. As regards the

* «“ Klements of Comparative Anatomy.”

MUCIFEROUS CANALS OF FISH. 183

muciferous canal, Schultze has suggested * that it is a
sense-organ adapted to receive vibrations of the water
with wave-leneths too great to be perceived as ordinary
sounds. Beard also leans to this same view. However
this may be, it is remarkably developed in many deep-
sea fish.

In some cases peculiar eye-like bodies are developed
in connection (though not exclusively so) with the
muciferous canal. lLeuckart,t by whom they were
discovered, at first considered them to be accessory
eyes, but subsequent researches led him to modify
this opinion, an to regard them as luminous organs.
Ussow{ has more recently maintained that they are
eyes, and Leydig considers them as organs which
approach very nearly to true eyes (“welche wirblichen
sehorganen sehr nahe stehen”). Whatever doubt there
may be whether they have:any power of sight, there is
no longer any question but that they are luminous,
and they are especially developed in the fishes of the
deep sea.

These are very peculiar. The abysses of the ocean
are quite still, and black darkness reigns. ‘The
pressure of the water is also very great.

Hence the deep seas have a peculiar fauna of their
own. Surface species covld not generally bear the
enormous pressure, and do not desceni to any great
depth. ‘The true deep-sea forms are, however, as yet
little known. They are but seldom seen, and when

* “Ueber die Sinnesorgane der Seitenlinie bei Fischen und
Amphibien,” Arch. fiir Mic. Anat., 1870.
t “ Ueber muthmassliche Nebenaugen bei einem Fische.” Bericht
tiber die 39 Vers., Deutscher Naturforscher, Giessen, 1864.
I “ Ueber den Bau der sog. augenahniichen Flecken einiger
Knochenfische,” Bull. Soc. Imp. Moscow, 1879.
10

184 DEEP-SEA FISH.

obtained are generally in a bad state of preservation.
Their tissues seem to be unusually lax, and liable to
destruction. Moreover, in every living organism,
besides those usually present in the digestive organs,
the blood and other fluids contain gases in solution.
These, of course, expand when the pressure is
diminished, and tend to rupture the tissues. The
circumstances under which some deep-sea fish have
occasionally been met with on the surface bears this
out. They are generally found to bave perished while
endeavouring to swallow some prey not much smaller,
or even in some cases larger, than themselves. What,
then, has happened? During the struggle they were
carried into an upper layer of water. Immediately
the gases within them began to expand, and raised
them higher; the process continued, and they were
carried up more and more ‘rapidly, until they reached
the surface in a dying condition.*

It is, however, but rarely that deep-sea fish are
found thus floating on the surface, and our knowledge
of them is mainly derived from the dredge, and
especially from the specimens thus obtained during
the voyage of the Challenger.

In other respects, moreover, their conditions of life
in the ocean depths are very peculiar. The light of
the sun cannot penetrate beyond about two hundred
fathoms; deeper than this, complete darkness prevails.
Hence in many species the eyes have more or less
completely disappeared. In others, on the contrary,
they are well developed, and these may be said to be
a light to themselves. In some species there are a
number of luminous organs arranged within the area

* Giinther, “ Introduction to the Study of Fishes.” _

as Sse ae ee aA

LIGHT-ORGANS. 185

of, and in relation to, the muciferous system; while in
others they are variously situated. These luminous
organs were first mentioned by Cocco.* They have
since been studied by Giinther, Leuckart, Ussow,
Leydig, and Emery. Lastly, they have been carefully
described by Giinther, Moseley, and von Lendenfeld
in the work on “ Deep-Sea Fishes,” in vol. xxvii. of
the “Challenger Reports.” The deep-sea fish are
either silvery, pink, or in many cases black, sometimes
relieved with scarlet, and, when the Inminous organs
flash out, must present a very remarkable appearance.

We have still much to learn as to the structure and
functions of these organs, but there are cases in
which their use can be surmised with some probability.
The light is evidently under the will of the fish. It is
easy to imagine a Photichthys (Fig. 114), swimming

Fig. 114.—Photichthys argenteus (‘‘ Challenger Reports,” vol. xxvii.).

in the black depths of the ocean, suddenly flashing out
light from its luminous organs, and thus bringing into
view any prey which may be near; while, if danger
is disclosed, the light is again at once extinguished.
It may be observed that the largest of these organs is
situated just under the eye, so that the fish is actually
provided with a bull’s eye lantern. In other cases

* Nuovi Ann. dei Sci. Nut., 1838.

186 LIVING LAMPS.

the light may rather serve as a defence, some having—
as, for instance, in the genus Scopelus—a pair of large
ones in the tail, so that “a strong ray of light shot
forth from the stern-chaser may dazzle and frighten an
enemy.” * In other cases they probably serve as lures.
The “sea-devil,” or “angler,” of our coasts has on
its head three long, very flexible, reddish filaments,
while all round its head are fringed appendages, closely
resembling fronds of seaweed. The fish conceals itself
at the bottom, in the sand or among seaweed, and
dangles the long filaments in front of its mouth.
Other little fishes, taking them for worms, Hea,
ingly approach, and themselves fall victims.

Several species of the same family live at great

Fig. 115.—Ceratius bispinosus (‘* Challenger Reports,” vol. xxvii.).

depths, and have very similar habits. A mere red
filament would, however, be invisible in the dark, and
therefore useless. ‘hey have, however, developed
(Fig. 115) a luminous organ, a living “ glow-lamp,” at

* Giinther, “ Challenger Reports,” vol. xxvii.

ee ae

Pore

ie ig tS ig

oe > Diack Maier. cr Pia “2

PROBLEMATICAL. ORGANS IN LOWER ANIMALS. 187

the end of the filament, which doubtless proves a very
effective lure.*

These cases, however, though very interesting, throw
little light on the use of the muciferous system
in ordinary fish, which, I think, still remains an
enigma.

In some of the lower animals, the nerves terminate
on reaching the skin at the base of rod-like structures
similar, in many respects, to the rods of the retina, or
the auditory rods of the ear, and of which it is very
difficult to say whether they are organs of touch or of
some higher sense.

Round the margin of the common sea-anemone is
a circle of bright blue spots, or small bladders. If a
section be made, there will be found a number of
cylindrical organs, each containing a fine thread, and
terminating in a “cnidocil (Fig. 14);” and, secondly,
fibres very like nerve-threads, swelling from time to
time with ganglionic expansions, and also terminating
in a enidocil. These structures, in all probability,
serve as an organ of sense, but what impressions they
convey it is impossible to say.

Some jelly-fishes (Trachynemade) have groups of
long hairs arranged in pairs at the base of the tentacles
(Fig. 116), which have been regarded as organs of
touch, and it is certainly difficult to suggest any other
function for them. They are obviously sense-hairs,
but I see no reason for attributing to them the sense
of touch.

The so-called eyes of the leech, in Leydig’s } opinion,

* Ginther, “ Study of Fishes.”
+ “Die Augen und neue Sinnesorgane der Egel.,” Reichert’s Arch.,
1861.

188 MEDUSZ—INSECTS—CRUSTACEA.

which is confirmed by Ranke,* are also developed from
the supposed special organs of touch. The latter are
much more numerous, as many as sixty being developed

Fig. 116.—Edge of a portion of the mantle of Aglawra hemistoma, with a pair of sense-
organs (after Hertwig). v, Velum; &, sense-organ; ro, layer of nettle cells; ¢,
tentacle.

on the head alone. They are cylindrical organs, lined
with large nucleated refractive cells, which occupy
nearly all the interior. A special nerve penetrates
each, and, after passing some way up, appears to
terminate in a free end.

I may also allude to the very varied bristles and
cirrhi of worms, with their great diversity of forms.

Among Insects and Crustacea, there are a great
number of peculiarly formed skin appendages, for
which it is very difficult to suggest any probable
function.

The lower antenne of the male in Gammarus, for
instance, bear a very peculiar slipper-shaped organ,
situated on a short stalk: this was first mentioned by

* “Beit. zu der Lehre. von den Uebergangs Sinnesorganen,” Zeit.
fiir Wiss. Zool., 1875.

DIFFICULTY OF PROBLEM. 189

Milne Edwards, and subsequently by other authors,
especially by Leydig.* The short stalk contains a
canal, which appears to divide into radiating branches

on reaching the “slipper,”
which itself is marked by a
series of rings.

Among other problematical
organs, I might refer to the
remarkable pyriform sensory
organs on the antenne of
Pleuromma,f the appendages
on the second thoracic leg of
Serolis, those on the maxilli-
peds of Kurycopa, on the me-
tatarsus of spiders, the finger-
shaped organ on the antenne
of Polydesmus, the singular
pleural eye (?) of Pleuromma,
and many others.

There is every reason to
hope that future studies will
throw much light on these in-

Fig. 117.—Sense-organ of leech
(from Carriére, after Ranke).
1, Epithelium; 2, pigment; 3,
cells; 4, nerve. The longer axis
equals °4 mm.

teresting structures. We may, no doubt, expect much
from the improvement in our microscopes, the use of
new reagents, and of mechanical appliances, such as
the microtome ; but the ultimate atoms of which matter
is composed are so infinitesimally minute, that it is
difficult to foresee any manner in which we may hope
for a final solution of these problems.

Loschmit, who has since been confirmed by Stoney
and Sir W. Thomson, calculates that each of the

* Zeit. fiir Wiss. Zool.,”’ 1878.

+ Brady, ‘On the Copepoda of the Challenger Expedition,” vol. viii.

190 SIZE OF ULTIMATE ATOMS.

ultimate atoms of matter is at most sy 505,00 Of an
inch in diameter. Under these circumstances, we
cannot, it would seem, hope at present for any great
increase of our knowledge of atoms by improvements
in the microscope. With our present instruments we
can perceive lines ruled on glass which are 55159 of an
inch apart. But, owing to the properties of light itself,
the fringes due to interference begin to produce con-
fusion at distances of 745, and in the brightest part
of the spectrum, at little more than 5559, they would
make the obscurity more or less complete. If, indeed,
we could use the blue rays by themselves, their waves
being much shorter, the limit of possible visibility
might be extended to ,5,!959; and, as Helmholtz has ©
suggested, this perhaps accounts for Stinde having
actually been able to obtain a photographic image of
lines only 45095 Of an inch apart. This, however,
would appear to be the limit, and it would seem,
then, that, owing to the physical characters of light,
we can scarcely hope for any great improvement so
far as the mere visibility of structure is concerned,
though in other respects, no doubt, much may be
hoped for. At the same time, Dallinger and Royston
Pigott have shown that, as far as the mere presence
of simple objects is concerned, bodies of even smaller
dimensions can be perceived. According to the views
of Helmholtz, the smallest particle that could be |
distinctly defined, when associated with others, is
about goh55 of an inch in diameter. Now, it has
been estimated that a particle of albumen of this size
contains 125,000,000 of molecules. In the case of such
a simple compound as water, the number would be
no less than 8,000,000,000. Even then, if we could

THE RANGE OF VISION AND OF HEARING. 191

construct microscopes far more powerful than any we
now possess, they could not enable us to obtain by
direct vision any idea of the ultimate molecules of
matter. The smallest sphere of organic matter which
could be clearly defined with our most powerful micro-
scopes may be, in reality, very complex; may be built
up of many millions of molecules, and it follows that
there may be an almost infinite number of structural
characters in organic tissues which we can at present
foresee no mode of examining.

Again, it has been shown that animals hear sounds
which are beyond the range of our hearing, and that
they can perceive the ultra-violet rays, which are
invisible to our eyes.”

Now, as every ray of homogeneous light which we
ean perceive at all, appears to us as a distinct color,
it becomes probable that these ultra-violet rays must
make themselves apparent to the ants as a distinct and
separate color (of which we can form no idea), but as
different from the rest as red is from yellow, or green
from violet. The question also arises whether white
light to these insects would differ from our white light
in containing this additional color. At any rate, as
few of the colors in nature are pure, but almost all
arise from the combination of rays of different wave-
lengths, and as in such cases the visible resultant
would be composed not only of the rays we see, but of
these and the ultra-violet, it would appear that the
colors of objects and the general aspect of nature
must present to animals a very different appearance
from what it does to us.

These considerations cannot but raise the reflection

* “ Ants, Bees, and Wasps.”

192 UNKNOWN SENSES.

how different the world may—I was going to say must
—appear to other animals from what it does to us.
Sound is the sensation produced on us when the vibra-
tions of the air strike on the drum of our ear. When
they are few, the sound is deep; as they increase in
number, it becomes shriller and shriller; but when they
reach 40,000 in a second, they cease to be audible.
Light is the effect produced on us when waves of light
strike on the eye. When 400 millions of millions of
vibrations of ether strike the retina in a second, they
produce red, and as the number increases the color
passes into orange, then yellow, green, blue, and violet.
But between 40,000 vibrations in a second and 400
millions of millions we have no organ of sense capable
of receiving the impression. Yet between these limits
any number of sensations may exist. We have five
senses, and sometimes fancy that no others are possible.
But it is obvious that we cannot measure the infinite
by our own narrow limitations.

Moreover, looking at the question from the other
side, we find in animals complex organs of sense, richly
supplied with nerves, but the function of which we are

s yet powerless to explain. There may be fifty other
senses as different from ours as sound is from sight;
and even within the boundaries of our own senses there
may be endless sounds which we cannot hear, and
colors, as different as red from green, of which we have
no conception. ‘These and a thousand other questions
remain for solution. The familiar world which sur-
rounds us may be a totally different place to other
animals. To them it may be full of music which we
cannot hear, of color which we cannot see, of sensations
which we cannot conceive. To place stuffed birds and

THE UNKNOWN WOKLD. 193

beasts in glass cases, to arrange insects in cabinets,
and dried plants in drawers, is merely the drudgery
and preliminary of study; to watch their habits, to
understand their relations to one another, to study
their instincts and intelligence, to ascertain their
adaptations and their relations to the forces of nature,
to realize what the world appears to them; these
constitute, as it seems to me at least, the true interest
of natural history, and may even give us the clue to
senses and perceptions of which at present we have no
conception,

CHAPTER Ix.
ON BEES AND COLORS,

In my book on “ Ants, Bees, and Wasps,’* I have
recorded a number of observations which seemed to
me to prove that bees possess the power of distinguish-
ing colors—a power implied, of course, in the now
generally accepted views as to the origin of the colors
of flowers, but which had not up to that time been
proved by direct experiment.

Amongst other experiments, I brought a bee to some
honey which I placed on a slip of glass laid on blue
paper, and about three feet off I placed a similar drop
of honey on orange paper. With a drop of honey before
ber a bee takes two or three minutes to fill herself, then
flies away, stores up the honey, and returns for more.
My hives were about two hundred yards from the
window, and the bees were absent about three minutes,
or even less; when working quietly they fly very quickly,
and the actual journeys to and fro did not take more
than afewseconds. After the bee had returned twice, I
transposed the papers; but she returned to the honey
on the blue paper. I allowed her to continue this for
some time, and then again transposed the papers. She

*« Ants, Bees, and Wasps,” International Scientific Series. Kegan
Paul, Trench & Co.

EXPERIMENTS WITH COLORED PAPERS. 195

returned to the old spot, and was just going to alight,
when she observed the change of color, pulled herself
up, and without a moment’s hesitation darted off to the
blue. No one who saw her at that moment could have
the slightest doubt about her perceiving the difference
between the two colors.

I also made a number of similar observations with
red, yellow, green, and white. But I was anxious to
carry the matter further, and ascertain, if possible
whether they have any preference for one color over
another, which had been denied by M. Bonnier. To
test this I took slips of glass of the size used for slides
for the microscope, viz. three inches by one, and pasted
on them slips of paper of the same size, coloured re-
spectively blue, green, orange, red, white, and yellow. I
then put them on a lawn, in a row, about a foot apart,
and on each put a second slip of glass with a drop of
honey. I also put with them aslip of plain glass witha
similar drop of honey. I had previously trained
a marked bee to come to the place for honey. My
plan then was, when the bee returned and had sipped
for about a quarter of a minute, to remove the honey,
when she flew to another slip. This I then took away,
when she went to a third,and soon. In this way, as
bees generally suck for three or four minutes, I induced
her to visit all the drops successively before returning
to the nest. When she had gone to the nest, I trans-
posed all the upper glasses with the honey, and also
moved the colored glasses. ‘Thus, as the drop of honey
was changed each time, and also the position of the
colored glasses, neither of these could influence the
selection by the bee.

In recording the results, I marked down successively

196 EXPERIMENTS WITH COLORED PAPERS.

the order in which the bee went to the different coloured
glasses. For instance, in the first journey from the
nest, as recorded below, the bee lit first on the blue,
which accordingly I marked 1; when the blue was
removed, she flew about a little, and then lit on the
white; when the white was removed, she settled on
the green, and so on successively on the orange, yellow,
plain, and red. I repeated the experiment a hundred
times, using two different hives—one in Kent and one
in Middlesex—and spreading the observations over
some time, so as to experiment with different bees, and
under varied circumstances.

I believe that the precautions taken placed the
colors on an equal footing, and that the number of ex-
periments is sufficient to give a fair average. More-
over, they were spread over several days, and the daily
totals did not differ much from one another. The
result shows a marked preference for blue, then white,
then successively yellow, red, green, and orange. The
red I used was a scarlet; pink would, I believe from
subsequent observations, have been more popular. I
may also observe that the honey on plain glass was
less visited than that on any of the colors, which was
the more significant because when I was not actually
observing, the colors were removed, and some drops
of honey left on plain glass, which naturally gave
the plain glass an advantage.

Another mode of testing the result is to take the
number of times in which the bee went first to each
color, for instance, in a hundred visits she came to the
blue first thirty-one times, and last only four; while to
the plain glass she came first only five times, and last
twenty-four times. It may be worth while to add that
I by no means expected such a result.

DR. MULLER’S OBJECTIONS. 197

A recent number of Kosmos contains a very courte-
ous and complimentary notice of these observations by
Dr. H. Miller, which, coming from so high an authority,
is especially gratifying. Dr. Miller, however, criticizes
some of the above-mentioned experiments, and remarks
that, in order to make the test absolutely correct, the
seven glasses should have been arranged in every
possible order, and that this would give no less than
5040 combinations. I did not, however, suppose that
I had attained to mathematical accuracy, or shown the
exact degree of preference; all 1 claimed to show was
the existence, and order, of preference, and I think
that, as in my experiments the position of the colors
was continually being changed, the result in this respect
would have been substantially the same.

Dr. Miller also observes that when a bee has been
accustomed to come to one place for honey, she returns
to it, and will tend to alight there whatever the color
may be; and he shows, by the record of his own
experiences, that this has a considerable influence.
This is so. Of course, however, it applies mainly to
bees which had been used for some time, and were
accustomed to a particular spot. I was fully alive to
this tendency of the bees, and neutralized it to a
considerable extent, partly by frequently changing the
bee, and partly by moving the glasses. While, how-
ever, | admit that it is a factor which has to be taken
into consideration, I do not see that it affords any
argument against my conclusions. The tendency would
be to weaken the effect of preference for any particular
color, and to equalize the visits to all the glasses. This
tendency on the part of the bees was, as my experiments
show, overborne by the effect produced upon them

198 REPLY TO OBJECTIONS.

by the color. So far, then, from weakening my con-
clusions, the fact, so far as it goes, tends to strengthen
them, because it shows that notwithstanding this
tendency the blue was preferred, and the honey on
colorless glass neglected. The legitimate conclusion
to be drawn seems, I confess, to me, not that my mode
of observation was faulty, but rather that the pre-
ference of the bees for particular colors is even some-
what greater than the numbers would indicate.

Next, Dr. Miller objects that when disturbed from
one drop of honey, the bees naturally would, and that
in his experiments they actually did, fly to the next.
Asa matter of fact, however, this did not happen in
mine, because, to avoid this source of error, when I
removed the color I gave the bee a good shake, and so
‘made her take a flight before settling down again.

According to my experience, bees differ considerably
in character, or, I should rather perhaps say, in humour.
Some are much shyer and more restless than others.
When disturbed from the first drop of honey, some are
much longer before they settle on the next than others.
Much also, of course, depends on how long the bee has
been experimented on. Bees, like men, settle down to
their work. Moreover, it is no doubt true that, ceteris
paribus, a bee in search of honey will go to the nearest
source.

But, as a matter of fact, in my hundred experiments
I had but very few cases like those quoted above from
Dr. Miller. This arose partly from the fact that my
bees were frequently changed, and partly because, as
already mentioned, I took care, in removing the color,
to startle the bee enough to make her take a little
flight before alighting again. Dr. Miller says that in

PREFERENCES OF BEES. 199

his experiments, when the bee did not go to the next
honey, it was when he shook her off too vigorously. I
should rather say that in his observations he did not
shake the bee off vigorously enough. ‘The whole
objection, however, is open to the same remark as the
last. The bee would have a tendency, of course, like-
any one else, to go to its goal by the nearest route.

- Hence I never supposed that the figures exactly indi-

cate the degree of preference. The very fact, however,
that there would naturally be a tendency on the part
of the bees to save themselves labour by going to the
nearest honey, makes the contrast shown by my
observations all the more striking.

I have never alleged that it was possible, in the case
of bees (or, for that matter, of men either), to get any

- absolute and exact measure of preference for one color

over another. It would be easy to suggest many con-
siderations which would prevent this. For instance,
something would probably depend on the kind of
flower the bee had been in the habit of visiting. A
bee which had been sucking daisies might probably
behave very differently from one which had been
frequenting a blue flower.

So far, however, as the conclusions which I ventured
to draw are concerned, I cannot see that they are in
any way invalidated by the objections which Dr.
Muller has urged, which, on the other hand, as it seems
to me, rather tend to strengthen my argument.

I may perhaps be asked, If blue is the favourite
color of bees, and then pink, and if bees have had so
much to do with the origin of flowers, how is it there
are so few blue and pink ones?

The explanation I believe to be that all blue flowers

200 THE COLORS OF FLOWERS.

have descended from ancestors in which the flowers
were red, these from others in which they were yellow,
while originally they were all green—or, to speak more
precisely, in which the leaves immediately surrounding
the stamens and pistil were green; that they have
passed through stages of yellow, and generally if not
always red, before becoming blue.

It is, of course, easy to see that the possession of color
is an advantage to flowers in rendering them more
conspicuous, more easily seen, and less readily over-
looked, by the insects which fertilize them ; but it is
not quite so clear why, apart from brilliancy and
visibility at a distance, one color should be more
advantageous than another. ‘These experiments how-
ever, which show that insects have their preference,
throw some hght on the subject.

Where insects are beguiled into visits, as is the case
especially with flies, they are obviously more likely to
be deceived if the flowers not only, as is often the case,
smell like decaying animal substance, but almost re-
semble them in appearance. Hence many fly flowers
not only emit a most offensive smell, but also are dingy
yellow or red, often mottled, and very closely resemble
in color decaying meat.

There remains another case in which allied flowers,
and species, moreover, which are fertilized by very much
the same insects, are yet characterized by distinct
colors. .We have, for instance, three nearly allied
species of dead neti!e—one white (Lameum album), one
red (Lamium maculatum), and one yellow (Lamiwm
galeobdolon or luteum).

Now, if we imagine the existence in a single genus
of three separate species, similar in general habit and

THE COLORS OF FLOWERS. 201

appearance, and yet mutually infertile, it is easy to
see that it would be an advantage to them to have
their flowers differently colored. The three species
of Lamium above mentioned may be growing together,
and yet the bees, without difficulty or loss of time, can
distinguish the species from one another, and collect
pollen and honey without confusing them together. On
the other hand, if they were similarly colored, the
bees could only distinguish them with comparative
difficulty, involving some loss of time and probably
many mistakes.

I have not yet alluded especially to white flowers.
They seem to stand in a somewhat special position.
The general sequence, as I have suggested, is from
ereen, through yellow and red, to blue. Flowers
normally yellow seldom sport into red or blue; those
normally red often sport into yellow, but seldom into
blue. On the other hand, flowers of almost any color
may sport into white. White is produced by the
absence of color, may therefore appear at any stage,
and will be stereotyped if for any reason it should prove
to be an advantage.*

* The genesis of the color is a large and interesting question. It
may be due to various causes, and is by no means always owing to the
presence of a different coloring matter. For instance, as Professor.
Foster has observed to me, many species of Iris occur in blue and
yellow forms. The yellow is largely, or wholly, produced by chroma-
toplacts, the purple or blue to cell-sap, and if the latter is absent the
yellow becomes apparent.

CHAPTER X,

ON THE LIMITS OF VISION OF ANIMALS.
ANTS AND COLORS.

I HAVE elsewhere * recorded a series of experiments on
ants with light of different wave-lengths, in order, if
possible, to determine whether ants have the power of
distinguishing colors. For this purpose I utilized the
dislike which ants, when in their nest, have for light.
Not unnaturally, if a nest is uncovered, they think they
are being attacked, and hasten to carry their young
away to a darker and, as they suppose, a safer place.
I satisfied myself, by hundreds of experiments, that if
I exposed to light the greater part of a nest, but left
any of it covered over, the young would certainly be
conveyed to the dark part. In this manner I satisfied
myself that the various rays of the spectrum act on
them in a different manner from that in which they
affect us; for instance, that ants are specially sensitive
to the violet rays.

But I was anxious to go beyond this, and to attempt
to determine whether, as M. Paul Bert supposed, their
limits of vision are the same as ours. We all know that

* “ Ants, Bees, and Wasps.” 5

THE ULTRA-VIOLET RAYS. 203

if a ray of white light is passed through a prism, it is
broken up into a beautiful band of colors, known as the
spectrum. To our eyes this spectrum, like the rainbow,
which is, in fact, a spectrum, is bounded by red at the
one end and violet at the other, the edge being sharply
marked at the red end, but less abruptly at the violet
But a ray of leht contains, besides the rays visible to
our eyes, others which are called, though not with
absolute- correctness, heat-rays and chemical rays.
These, so far from falling within the linits of our vision,
extend far beyond it, the heat-rays at the red end, the
ehemical or ultra-violet rays at the violet end.

I made a number of experiments which satisfied me
that ants are sensitive to the ultra-violet rays, which
lie beyond the range of our vision. I was also anxious
to see how two colors identical to our eyes, but one
of which transmitted and the other intercepted the
ultra-violet rays, would affect the ants.

Mr. Wigner was good enough to prepare for me a
solution of iodine in bisulphide of carbon, and a second
of indigo, carmine, and roseine mixed so as to produce
the same tint. T’o our eyes the two were identical both
in color and capacity; but of course the ultra-violet
rays were cut off by the bisulphide-of-carbon solution,
while they were, at least for the most part, transmitted
by the other. I placed equal amounts in flat-sided
glass bottles, so as to have the same depth of each
liquid. I then laid them, as in previous experiments,
over a nest of Mornica fusca. In twenty observations
the ants went seveuteen times in all under the iodine
and bisulphide, twice under the solution of indigo
and carmine, while once there were some under each.
These observations, therefore, show that the solutions,

204 PERCEPTION OF LIGHT

though apparently identical to us, appeared to the ants
very different, and that, as before, they preferred to
rest under the liquid which intercepted the ultra-violet
rays. In two or three cases only they went under the
other bottle ; but I ought to add that my observations
were made in winter, when the ants were rather
sluggish. I am disposed to think that in summer
perhaps these exceptional’ cases would not have
occurred, |

Professor Graber, however, while admitting the
accuracy of my observations, has attempted to prove

that the perception of the ultra-violet rays is not a
case of sight in the ordinary acceptation of the words,
but is due to the general sensitiveness of the skin.

It has long been known that some of the lower
animals which do not possess eyes are, nevertheless,
sensitive to light. Hoffmeister,* in his work on earth-
worms, states that, with some exceptions, they are
very sensitive to light. Darwin, perhaps, experimented
with a different species (for there are many different
kinds); at any rate, his specimens seemed to be less
keenly affected, though it one was suddenly illumi-
nated it dashed “like a rabbit into its burrow.” He
observed, however, that some individuals were more
sensitive to light than others, and that the same indi-
viduals by no means always acted in the same way.
Moreover, if they “were employed in dragging leaves
into their burrows or in eating them, and even during
the short intervals when they rested from their work,
they either did not perceive the light or were regard-
less of it.”t He observes, however, that it is only the

* “ Wamilie der Regenwiirmer,” 1845.
+ Darwin’s ‘“ Earthworms.”

=.

BY THE GENERAL SURFACE OF THE SKIN. 205

anterior extremity of the body, where the cerebral
ganglia lie, which is affected by light, and he suggests
that the light may pass through the skin and acts
direetly on the nervous centres.

Lacaze-Duthiers, Haeckel, Engelmann, Graber,
Plateau, and other naturalists have abundantly proved
the sensitiveness to light of other eyeless animals.

There has, indeed, long been a vague idea that blind
people have some faint perception of hght through the
general surface of the skin. So far as 1 am aware
there is not the slightest evidence or foundation for this
belief; nor, indeed, has it been advocated by any com-
petent authority. It seems @ priort improbable that
an animal with complex eyes should still retain a
power which would be almost entirely useless.

On the other hand, it is unquestionable that light
ean, and often dves, act directly on the nerve termi-

nations without the intermediate operation of any

optical-apparatus.

Some of them might, perhaps, be open to criticism.
The effect of heat may not have been always sufficiently
guarded against. Again, it is quite true that, as Plateau
observes “ Lorsque les Myriapudes chilopodes aveugles
ou manis d’yeux, déposés sur le sol, s’introduisent avec
empressement dans la premiere fente quwils rencon-
trent, cet acte n’est pas déterminé par le seul besoin de
fuir la lumiére, ces animaux cherchent en méme temps
un milieu humide et avec lequel la plus grande parte
de la suriace de leur corps soit en contact direct.”
Bnt though this is no doubt true, and though, perhaps,
the moisture may be some help, still, whatever be their

* Plateau, *‘ Rech. sur la perception de la lumiére par les Myriapodes
aveugles,” Jour. del’ Anatomie, etc., T. xxii. 1886.

206 PERCEPTION OF LIGHT

object, we can hardly doubt that the absence of light is
the principal guide.

Professor Graber,* in his interesting memoir on
this subject confirms the observations on ants and
Daphnias, in which I showed that they are sensitive to
the ultra-violet rays, by similar observations on earth-
worms, newts, etc. It is interesting, moreover, that the
species examined by him showed themselves, like the
ants, specially sensitive to the blue, violet, and ultra-
violet rays. Graber, however, states that he differs
from me inasmuch as I attribute the sensitiveness to
the ultra-violet rays exclusively to vision ;—that it is
“ausschliesslich durch die Augen vermittelt.”. I am
not, however, of that opinion as a general expression,
though I believe it to be true of ants, where the
opacity of the chitine renders it unlikely that the light
could be perceived except by the medium of the eyes
or ocelli.

Graber has shown in earthworms and newts, and
Plateau in certain Myriapods, that these animals
perceive the difference between light and darkness by
the general surface of the skin. But more than this,
Graber seems to have demonstrated that earthworms
and newts distinguish not only between light of differ-
ent intensity, but also between rays of different wave-
lengths, preferring red to blue or green, and green to
blue. He found, moreover, as I did, that they are
sensitive to the ultra-violet rays. Harthworms, of
course, have no eyes; but, thinking that the light might

* «Fundamental Versuche iiber die Helligkeits und Farben Em-
pfindlichkeit augenloser und geblendeter Thiere,” Sitz. Kats. Akad.
d. Wiss. Wien: 1883.

+ Journ. de V Anatomie et de la Physiologie, 1886.

BY THE GENERAL SURFACE OF THE SKIN. 207

act directly on the cephalic ganglia, Graber decapi-
tated a certain number, and found that the light still
acted on them in the same manner, though the differ-
ences were not so marked. He also covered over the
eyes of newts, and found that the same held good with
them. |

Hence he concludes that the general surface of the
_ skin is sensitive to light. These results are certainly
curious and interesting, but even if we admit the
absolute correctness of his deductions, I do not see that
they are in opposition to those at which I had arrived.
My main conclusions were that ants, Daphnias, etc.,
were able to perceive light of different wave-lengths,
and that their eyes were sensitive to the ultra-violet
rays much beyond our limits of vision. His observa-
tions do not in any way controvert these deductions;
indeed, the argument by which he endeavours to prove
that the effect is due to true light, and not to warmth,
presupposes that sensations which can be felt by the
general surface of the skin, would be still more vividly
perceived by the special organs of vision.

In connection with this subject, I may add that I do
not at all doubt the sensitiveness to light of eyeless
animals. In experimenting on this subject, I have
always found that though the blind woodlice (Platy-
arthrus), which live with the ants, have no eyes, yet if
part of the nest be uncovered and part kept dark,
they soon find their way into the shaded part. It is,
however, easy to imagine that in unpigmented animals,
whose skins are more or less semi-transparent, the
light might act directly on the nervous system, even
though it could not produce anything which could be
called vision.

11

208 EXPERIMENTS WITH HOODWINKED ANTS.

Forel, in some recent experiments, varnished over
the eyes of fifteen ants (Camponotus ligiuperdus) and
put them with fifteen others, which were left in their
normal condition, in a flat box with a glass top and
divided in the middle into two halves by a cardboard
division, which, however, left room enough underneath
for the ants to pass freely from one half to the other.
After some.other experiments, in the course of which
one of the varnished ants was accidentally killed, at
1 p.m. all the varnished ants and thirteen of the un-
varnished were in the right half of the box, and two
unvarnished in the left. He then placed over the
whole box two flat bottles containing water to inter-
cept heat-rays—over the right half a piece of cobalt
(violet) glass; and over the left, a flat bottle containing
a solution of esculine, which is quite transparent, but
cuts off the ultra-violet rays. At 1.55 the result was
as follows :—

Under the esculine. Under the cobalt.
5 varnished. 9 varnished.
13 normal. 2 normal.

~The esculine and cobalt were then transposed. At
2.0 the position was—

Under the cobalt. Under the esculine.
4 varnished. 13 varnished.

3 normal. 12 normal.

The esculine and cobalt were again transposed, and
one normal ant was accidentally wounded and removed.

At 3.8—

Under the esculine. Under the cobalt.
3 varnished. 12 varnished.
11 normal. 3 normal.

F
4

EXPERIMENTS WITH HOODWINKED ANTS. 209

The esculine and cobalt were once more transposed,
and at 3.13 there were—

Under the cobalt. Under the esculine.
3 varnished. 11 varnished,
1 normal. 13 normal.

Thus the number of ants which followed the esculine
and moved from one half of the box to the other at
each transposition of the esculine and cobalt, was as
follows :—

Varnished. Normal.

First change ... oe 4) 1i
Second ,, Ee mee cee a wes et 20
Third, .,, ods ie? ean,» Oye ue 9
Fourth ,, ae wee BO filed | Ae 2. ee ee
6 40

And the number remaining under the —— and
esculine respectively was—

Under the cobalt. Under the esculine.

Varnisned. Normal. Varnisned. Normal
First experiment ... sae BES 2 5 13
Second ,, cate sigh tei 3 10 12
Third ay ea de oe Es aan te 3 1]
Fourth ., 3 | Lauer’ ated! iS
28 9 30 49

These experiments clearly showed that, while the
normal ants moved from side to side so as to be under
the esculine and consequently protected from the ultra-
violet rays, those in which the eyes had been varnished
remained unaffected by the transposition of the esculine
and -the cobalt, showing that the difference was per-
ceived, not by the general surface of the skin, but by
the eyes, and that when these were covered the ants
were unafie:ted by the change,

210 CONFIRMATION OF MY EXPERIMEN'S ON ANTS.

It might be suggested that possibly the ants had
been injured or stupefied by the varnishing. M. Forel
accordingly, on the following day at 8 a.m., placed over
one half of the box a layer of water six centimetres
deep, and on the other a piece of red glass, which,
while intercepting some of the licht, allows almost all
the heat to pass through. At 9.25 there were—

Under the red glass. Under the layer of water.
3 varnished. 11 varnished.
12 normal. 2 normal.

Here, it seems that the ants which could see pre-
ferred the shade, even though they were rather too
warm; while the hoodwinked ants went under the
cool water.

This indicated that the varnished ants remained
sensitive to heat, though not to light. Indeed, Forel
states that they were just as lively, just as sensitive to
currents of air, as the normal ants.*

These experiments, then, entirely confirm those I
had made. “Cvest une confirmation entiére,’ says
Forel, “des resultats de Lubbock ft” and he sums upas
follows :—The ants “paraissent percevoir l’ultra-violet
principalement avec leurs yeux, c’est-a-dire qu’elles le
volent, car lorsque leurs yeux sont vernis elles s’y
montrent presque intifférentes; elles ne réagissent
alors nettement qun’d une lumiere scolaire directe ou
moins forie. Les expériences ci-dessus semblent in-
diquer que les sensations dermatoptiques sont plus

faibles chez les fuurmis que chez les animaux étudiés —

par Graber.”
From these and other experiments M. Forel comes

* Loe: ctt.; p. bot. { Ibid., p. 174.

ier. we se

EXPERIMENTS WITH DAPHNIAS. > pl |

to the same conclusion as I did, that the ants perceive
the ultra-violet rays with their eyes, and not as suggested
by Graber, by the skin generally. It is very gratifying
that my experiments and conclusions should thus be
entirely confirmed by an observer so careful and so
experienced as M. Forel.

/

F ~
>
;
;

PF OES My ei
’ ¥ 2

a ee

Fig. 118.—Daphnia pulex. a, Antenne; b, brain; e, eye; h, heart; m, muscle of
- eye; m, nerve of eye; 0, Ovary; ol, olfactory organ; s, stomach; y, three eggs
deposited in the space between the back and the shell.

EXPERIMENTS WITH DAPHNIAS.

The late M..Paul Bert made some very interesting
experiments on a small fresh-water crustacean belong-

ds Fei ia

rd ib DAPHNIAS AND COLORS.

ing to the genus Daphnia (Fig. 118), from which he
concludes that they perceive all the colors known to us,
being, however, especially sensitive to the yellow and
green, and that their limits of vision are the same as ours.

Nay, he even goes further than this, and feels justi-
fied in concluding, from the experience of two species
—Man and Daphnia—that the limits of vision would
be the same in all cases.

His words are—

1. “Tous les animaux voient les rayons spectraux
que nous voyons.”

2. “Ils ne veient aucun de ceux que nous ne voyons
pas.” :

3. “ Dans l’étendue de la région visible, les différences
entre ies }ouvoirs éclairants des différents rayons
colorés sont les mémes pour eux et pour nous.”

He also adds, “Puisque les limites de visibilité
semblent étre les mémes pour les animaux et pour
nous, ne trouvons-nous pas 1& une raison de plus pour
supposer que le réle des milieux de l’ceil est tout a fait
secondaire, et que la visibilité tient a limpression-
nabilité de l'appareil nerveux lui-méme ?”

These generalizations would seem to rest on a very
narrow foundation. I have already attempted to show
that the conclusion does not appear to hold good in the
case of ants; and I determined, therefore, to make some
experiments myself on Daphnias, the results of which
are here embodied.”

Professor Dewar was kind enough to arrange for me, at
the Royal Institution, a spectrum, which, by means of a
mirror, was thrown on to the floor. I then placed some

* These observations were published in the Journal of the Linnean
Suciety for 1881.

PREFERENCE FOR YELLOWISH GREEN. 213

Daphnias in a shallow wooden trough fourteen inches
by four inches, and divided by cross partitions of glass
into divisions, so that I could isolate the parts illumi-
nated by the different coloured rays. The two ends of
the trough extended somewhat beyond the visible
spectrum. I then placed fifty specimens of Daphnia
pulex in the trough, removing the glass partitions so
that they could circulate freely from one end of the
trough to the other. Then, after scattering them
equally through the water, I exposed them to the
light for ten minutes, after which I inserted the glass
partitions, and then counted the Daphnias in each
division. The results were as follows :—

NUMBER OF DAPHNIAS.

In the In the Beyond
Beyond red and _ greenish yellow Inthe In the the

the red. yellow. and green. blue. violet. violet.
Obs. 1 0 20 28 2 () 0
2 1 21 25 3 0 0
> eae 21 D4 3 0 0
ee | 19 29 1 0 0
OE a 20 27 3 0 0
4 101 133 12 0 0

I may add that the blue and violet divisions were
naturally longer than the red and green.

May 25.—Tried again the same arrangement, but
separating the yellow, and giving the Daphnias the
choice between red, yellow, green, blue, violet, and

dark :—

Dark. Violet. Blue. Green. Yellow. Red.
Exp. 1 ae 0 3 39 4) 3
2 a0) 1 y) 37 i 3
os 0 0 4 31 10 5
4 id) 1 5 30 8 6
5 0 1 4 33 6 6

1) 3 18 170 36 23

214 EXPERIMENTS.

Of course, it must be remembered that the yellow band
is much narrower than the green. I reckoned as yellow
a width of three-quarters of an inch, and the width of
the green two inches.

Again— {
Dark. Violet. Blue. Green. Yellow. Red.
Pixies. pcsetee 0 = 30 6 10
ee oye - 0 if 3 23 8 45
was ee 0 0 2 24 9 15
ns Oe ee ey 0 3 25 8 13
te ca 10 1 2 24 ‘ih 16
1 2 14 128 38 67
Adding them to- — _— = aa — —
gether, we get 1 3) 32 298 4 90

M. Paul Bert observes (oc. ct.) that in his experiments
the Daphnias followed exactly the brilliance of the
light. It will be observed, however, that in my expe-
riments this was not the case, as there were more
Daphnias in proportion, as well as absolutely, in the
green, although the yellow is the brightest portion of
the spectrum. In fact, they follow the light up tea
certain brightness; but, as will be seen presently, they
do not like direct sunshine.

I then arranged the trough so that the yellow fell in
the middle of one of the divisions. The result was—

NUMBER OF DAPHNIAS.

Upper edge.
Ultra-red of red, Greenish
and yellow, and blue and Ultra-
lower red. lower green. blue. Violet. violet.
pty. a. 8 38 4 0 0
99 2 eee eae 9 36 5 0 0
ee ae 39 3 0 0
25 113 12 0 0

May 18.—In order to test the limits of vision at the

LIMITS OF VISION OF DAPHNIAS. 215

red end of the spectrum, I used the same arrangement
as before, placing the trough so that the extreme
division was in the ultra-red, and the second in the red.
I then placed sixty Daphnias in the ultra-red. After
five minutes’ exposure, 1 counted them. There were in
the—
Red. Ultra-red.
ee, ak an SE eu oR
Be ee ae i Senge
I now gave them four divisions to select from—dark,
red, ultra-red, and dark again. The numbers were—

Dark. Red. - Ultra-red Dark.
Bxpil, ... en aoe ie 47 6 2
Mee 41 7 3

I then shut them off from all the colors excepting

red, giving them only the ae between red and
ultra-red :—

Red Ulira-red.
Bxpo tl) uss ane aoe ee +
> Seer é Feats 3
_ 3 a ee reer © 6

I then left them access to a division on the other side
of the red, which, however, I darkened by interposing a
piece of wood. ‘This enabled me better to compare the
ultra-red rays with a really dark space :—

Dark. Red. Ultra-red.

eee tg eg 43 3
Ee OS tn Oe eine 45 2

These observations appear to indicate that their
limits of vision at the red end of the spectrum coincide
approximately with ours.

I then proceeded to examine their behaviour with
reference to the other end of the spectrum.

In the first place, I shut them off from all the rays

216 PERCEPTION OF ULTRA-VIOLET RAYS

except the blue, violet, and ultra-violet.
was as follows :—

NUMBER OF DAPHNTAS.

Ultra-violet. Violet. Blue.

Bien. AS Gees oe Be et 9 38
99 2 eee ece eee 4 6 38
33 3 oe3 e703 ees 0 2 46

9) 17 122

The result

a | wrwr

This shows that they greatly prefer blue and violet to

darkness or ultra-violet.

I afterwards gave them only the option of ultra-violet,

violet, and darkness :—

Ultra-violet. Violet.

Exp. 1 ste cae aac rae 48
ee ee OR te Lg 48
ses oe Cee ee ee ee 47
ee ee ees 42
ae ce aa ee: 53

49 238

D

1g

They preferred the violet; but there were many

more in the ultra-violet than in the dark.

I then tried ultra-violet and dark. The width of the
violet was two inches; and I divided the ultra-violet
portion again into divisions each of two inches, which
we may eall ultra-violet, further ultra-violet, and still

further ultra-violet. The results were—

NUMBER OF DAPHNIAS.
Still further Further

ultra-violet. ultra-violet. Ultra-violet.

[ec Ole omens 0 6 52
i es 0 5 52
eee, 0 6 50
sg) vero PRS 0 4 53
bb) 5) tae ss8 0 4 54

a ee
286

Da

Ff

fod
i» | no oo oe BD

. ———s

PERCEPTION OF ULTRA-VIOLET RAYS. SET

In this case the preference for ultra-violet over dark

was very marked.

May 18.—I again tried them with the ultra-violet
rays, using three divisions—namely, further ultra-violet,
ultra-violet, and dark. The numbers were as follows,
viz. under the—

Further
ultra-violet. Ultra-violet. Dark,
wee see “ee A 50 4.
39 2 eer aes eee 3 5 5 2
9 105 6

To my eye there was no perceptible difference be-
tween the further ultra-violet and the ultra-violet
portion; but slightly undiffused light reached the two
extreme divisions. It may be asked why the still
further ultra-violet division should have been entirely
deserted, while in each case two or three Daphnias were
in the darkened one. This, I doubt not, was due to the
fact that, the darkened division being next to the ultra-
violet, one or two in each case straggled into it.

Not satisfied with this, I tried another test. There are
some liquids which, though transparent to the rays
we see, are quite opaque to the ultra-violet rays.
Bisulphide of carbon, for instance, is quite colourless
and transparent: it looks just like water, but it entirely
euts off the ultra-violet rays. If, then, we place the
trough containing Daphnias, as I had previously done
my nest of ants, in the ultra-violet part of the spectrum,
and then place over one half of it a flat bottle contain-
ing water, and over the other half a similar bottle con-
taining bisulphide of carbon, both halves will seem
equally dark to us, but the ultra-violet rays reach one
half of the vessel, while they are cut off from the other.

218 PERCEPTION OF ULTRA-VIOLET RAYS.

To our eyes both, as I say, are equally dark, and so they
would be to the Daphnias if their limits of vision were
the same as ours. As a matter of fact, however, the
Daphnias all collected in the part of the trough under
the water, and avoided that under the bisulphide of car-
bon, showivg that this, therefore, was to them darker
than the other. I varied the experiments in several
ways, but always with similar results. Bichromaie of
potash is also impervious to the ultra-violet rays, and
had the same effect.

Not satisfied with this, I tried to test it in another
way.

I took a cell, in which I placed a layer of five-per-
cent. solution of chromate of potash less than an eighth
of an inch in depth, and which, though almost colourless
to our eyes, completely cut off the ultra-violet rays. IL
then turned my trough at right angles, so that I could
cover one side of the ultra-violet portion of the spectrum
with the chromate and leave the other exposed. The
numbers were as follows :—

Side of the ultra- -
violet covered with Side
chromate of potash. uncovered. Dark.

Exp. 1 sas. bee 2 ey — aH) a 0
I now covered up the other side.

Min 2 52. ae Sek OS gee
Again covered up the same side as at first.

Hep. 3 Oko it ga ae ee
Again covered up the other side.

Hp Ai sc. nen Stee Jen 57 eae 0

May 19.—I again tried the same arrangement, re- |
ducing the chromate of potash to a mere film, which,

OBJECTIONS OF M. MEREJKOWSKY. 219

however, still cut off the ultra-violet rays. Ithen placed
it, as before, over one half of the ultra-violet portion of
the spectrum ; and over the other half I placed a similar
cell containing water. Between each experiment I
reversed the position of the two cells. The numbers
were—

Under the film of Under the

chromate of putash. water.
Map l. ... ae a es it aie 52
De ES ee eee re eee
ee IG ig ne ges 1g BO
ol Saaere ae taal | =5E wa 23

Evidently, then, even a film of chromate of potash
exercises a very considerable influence; and, indeed, L
doubt not that, if a longer time had been allowed, the
difference would have been even greater.

It seems clear, therefore, that a five-per cent. solution
of chromate of potash only one-eighth of an inch in
thickness, which cuts off the ultra-violet rays, though
absolutely transparent to our eyes, is by no means so to
the Daphnias.

These observations seem to prove, though I differ
with great reluctance from so eminent an authority as
M. Paul Bert, that the limits of vision of Daphnias do
not, at the violet end of the spectrum, coincide with
ours, but that the Daphnia, like the ant, is affected by
the ultra-violet rays. |

Since these observations were published, M. Merej-
kowski has experimented on the subject, and come
to the conclusion that the Daphnias are attracted
wherever there is most light, that they are conscious
only of the intensity of the light, and that they have no
power of distinguishing colors. It is no doubt true
thatin ordinary diffused daylight the Daphnias generally

220 DAPHNIAS SUPPOSED TO PERCEIVE

congregate wherever the light is strongest. Their eyes
are, however, so delicate that one would naturally expect,
a priort, that there would be a limit to this; and, in
fact, direct sunshine is somewhat too strong for their
comfort.

For instance, I took a porcelain trough, seven and a
half inches long, two and a half broad, and one deep, and
put in it some water containing fifty Daphnias. One
half I exposed to direct sunlight, and the other I shaded,
counting the Daphnias from time to time, and trans-
posing the exposed and shaded halves. The numbers
were as follows:—

In the sun. -In the shado.

At 10.40 am. ... aid ae Ee aoe 46
age a | Mee 8 42
Rai bs 7 43
ML Baye: 7 43
Se Vie, ty 4 46
5B 3 47
Ae 8 ag. 4 46
Sas 5 45
es aN 7 43
PP) 4 30 3) 4 e 46

53 447

This seems clearly to show that they avoid the full
sunlight.

I believe, then, that in some of my previous experi-
ments the yellow light was too brilliant for them; and
the following experiments seem to show that, when
sufficiently diffused, they prefer yellow to white light.

M. Merejkowsky, however, denies to the crustacea
any sense of color whatever. His experiments were
made with larve of Balanus and with a marine cope-
pod, Dias longiremis. ‘These, if I understand him
correctly, have given identical results. He considers

BRIGHTNESS, BUT. NOT COLOR. oa

that they perceive all the luminous rays, and can dis-
tinguish very slight differences of intensity; but that
they do not distinguish between different colors. He
sums up his observations as follows :—

“Tl résulte de ces expériences que ce qui agit sur les
Crustacés, ce n’est point la qualité de la lumiére, c’est
exclusivement sa quantité. Antrement dit, les Crus-
tacés inférieurs ont la perception de tonte onde lumi-
neuse et de toutes les différences, méme trés légéres, dans
son intensité; mais ils ne sont point capabies de dis-
tinguer la nature des ondes, de différentes couleurs. Ils
distinguent tres bien lintensité des vibrations éthérées,
leur amplititde, mais point leur nombre. Il y a donc,
dans le mode de perception de la lumiére, une grande
différence entre les Crustacés inférieurs et 1’ Homme, et
méme entre eux et les Fourmis; tandis que nous
voyons les différentes couleurs et leurs différentes
intensités, les Crustacés inférieurs ne voient qu'une
seule couleur dans ses différentes variations d’intensité.
Nous percevons des couleurs comme couleurs; ils ne
les pergoient que comme lumieére.” *

It is by no means easy to decide such a question
absolutely ; but the subject is of much interest, and
accordingly I made some further experiments, as it did
not seem to me that those of M. Merejkowsky bore out
the conclusion he has deduced from them. 7

Professor Dewar most kindly arranged the apparatus
for me again. He prepared a normal diffraction-spec-
trum, produced by a Rutherfurd grating with 17,000 —
lines to the inch; the spectrum of the first order was
thrown on the trongh. In this case the distribution of

* M. C. Merejkowsky, “ Les Crustacés inférieurs distinguent-ils les
couleurs ?”

oD, FURTHER EXPERIMENTS.

luminous intensity has been shown to be uniform on
each side of the line having the mean wave-length, z.e.
a little above the line D in the yellowish green of the
spectrum.

I then took a long shallow trough in which were
a number of Daphnias, and placed it so that the
centre of the trough was at the brightest part of
the spectrum, a little, however, if anything, towards
the green end. After ee the Daphnias equably
I left them for five minutes, and then put a piece of
blackened cardboard over the brightest part. After
five minutes more, there were at the green end, 410;
in the dark, 14; at the red end, 76. Here the two
ends of the trough were equally illuminated; but
the preference for the green over the red side was very
marked,

I then took five porcelain vessels, seven and a half
inches long, two and a half broad, and one deep, and
in each I put water containing fifty Daphnias. One
half of the water I left uncovered; the other half IL
covered respectively with an opaque porcelain plate, a
solution of aurine (bright yellow), of chlorate of copper
(bright green), a piece of red glass, and a piece of blue
glass. Every half-hour I counted the Daphnias in
each half of every vessel, and then transposed the
coverings, so that the half which had been covered was
left exposed, and vice versé. I also changed the Daph-
nias from time to time.

Here, then, in each case the Daphnias had a choice
between two kinds of light. It seemed to me that this
would be a crucial test, because in every case the
colored media act by cutting of certain rays. Thus
the aurine owes its yellow color to the fact that it cuts

FURTHER EXPERIMENTS. Qe

off the violet and blue rays. The light beneath it con-
tains no more yellow tays than elsewhere; but those
rays produce the impression of yellow, because the
yellow is not neutralized by the violet and blue. In
each case, therefore, there was less light in the covered
than in the uncovered part.

After every five experiments I added up the number
of the Daphnias; and the following table gives twenty
such totals, each containing the result of five observa-

tions, making in all one hundred.

_ My reason for adding one vessel in which one half
had an opaque cover was to meet the objection that
possibly the light might have been too strong for the
Daphnias; so that when they went under the sheltered
part they did so, not for color, but for shade. I was
not very sanguine as to the result of this arrangement,
because I had expected that the preference of the
Daphnias for light would overcome tieir attachment to
yellow.

The numbers were as in the following table (p. 224).

The result was very marked. The first two columns
show the usual preference for light. If the covered
half had been quite dark, no doubt the difference in
numbers would have been greater; but a good deal of
light found its way into the covered half. Still the
result clearly shows that the Daphnias preferred the
lighter half. The numbers were 2048 in the dark to
2952 in the light; and it will be seen that the preference
for the light was shown, though in different degrees, in
almost every series.

The result in the blue gives, I think, no evidence as
to color-sense. The numbers were respectively 2046
against 2954, and were therefore practically the same —

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SVINHdUVd HfO YHAWON

PERCEIVE DIFFERENCES IN COLOR. D25

as in the preceding set. Since, however, a certain
quantity of light was transmitted through the blue, the
result may indicate a want of sensitiveness to the blue
rays. ,

In the red the numbers were 1928 as against 3072.

As regards the yellow, the results were very different,
the numbers being, under the yellow, 3096; in the
uncovered part, 1904. Here, therefure, we see a very
distinct preference, all the more remarkable because
the amount of light was really less than in the un-
covered part.

In the green the numbers were much more equal,
namely, 2406 against 2594. Here also the love for green
neutralized the preference for light. I do not, however,
wish for the moment to draw any conclusion from these
last figures, though I give them for what they are worth.
The coloured medium was, I believe, somewhat too
opaque. With a more transparent green, as will be
seen subsequently, the result would have been very
different.

At any rate, the above observations seemed to show a
marked preference for yellow. Still, [thought it might
be objected that, though the Daphnias obviously pre-
ferred the uncovered to the shaded half of the vessel,
and the yellow to the uncovered half of the vessel,
perhaps in the former the uncovered water was rather
too bright, and in the latter the shaded part was rather
too dark, and that after ali the yellow was chosen, not
because it was yellow, but because it hit off the happy
medium of intensity. The suggestion is very improb-
able, because the observations were made on several
successive, and very different, days, and at very
different hours. I also thought that the green was

226 EVIDENCE THAT DAPHNIAS

perhaps too dark; I took, therefore, a lighter tint, and
rearranged my little apparatus as follows :—

I placed (March 26) fifty Daphnias in a trough (1),
covering over one half of it with a pale green, and
another fifty in a trough (2) half of which was covered
with yellow (aurine). On one side was a similar trongh
(8), one end of which was shaded by a porcelain plate;
and on the other side a fourth trongh (4), one end of
which had a little, though but little, extra hght thrown
on it by means of a mirror. As before, I counted the
Daphnias from time to time, and turned the troughs
round, All four were in a light room, but not actually
in direct sunshine. Thus, then, in one trough I had
half the water in somewhat green light; in the second
trough, half the water in yellow light; in the third,
one half was exposed and the other sumewhat darkened ;
while the fourth, on the contrary, gave me a contrast
with somewhat more vivid light. If, then, the
Daphnias went under the green and yellow glass. not
on account of the color, but for the sake of shade,
then in trough 3 a majority of them would have gone
under the porcelain plate. On the other hand, if the
porcelain plate darkened the water too much, and yet
the open water was rather too light for the Daphnias,
then in the fourth trough they would, of course, have
avoided the illuminated half. The results show that
the third trough was unnecessary, still, 1 may as well
give the figures; the fourth proves that the Daphnias
preferred a light somewhat brighter than the ordinary
diffused light of the room. Of course, it does not follow
that the effect of color is the same as with us.

— eo Se

PERCEIVE DIFFERENCES OF COLOR. 297

TROUGH 1. | TROUGH 2. TrouGH 3. TROUGH 4,
Gieon White | Yellow | White ti eo ee Hlumi- | Unillu-
light. | light. | light. | Bele | bales |e pales | Sheek | minated
oe ha | cates SB
March 27. |
Sees) 75 | 38 | 17 35 Pee 98° | 90
mee) so | is | 28 | 22 37 eo aa oe
fap.) 27 | 293 | 38 | 17 36 FEO] ase | 25
eo ss | 17 | 3s | 17 38 12 | 30 | 20
me) og | on | 49 8 25 15 | ee bas
t= | 97 | te9 |" St |} 181 69 | 145 | 105
ee eeeh| 14 | a6 | 14 26 os) ag 1S
a | 44 ee Seren ae O4 96 | 23 | 27
eae {9 | 34° | 16 35 * Pig Ghee ota (eer
Mee | 1S | 25 | 25 3] 19 | 298 | 99
540...| 30 | 29 | 35 | 15 39 ig | 27 | 923
1733 | 77 |148 |102 | 149 | 101 | 148 | 102
March 28.
oe) 3s | 17-| «34 | 1I6 35 15 | 30 | 20
mae) 29 | is | 37 |. 13 27 23 | 32 | 18
io 2) 34 | ie | 33 | 17 29 21 | 30 | 20
eee aq | 34. |, 35 | 15 26 ose. |. 17
eee se | 94 | 97 | 28 33 te} se | eS
fee) ga | 166 | 84 | 150 |: 100 | 160 | 90
March 29. |
ens | 09 | 25 | 25 25 of :| 90 |. te
935 ...1 30 | 20 | 27 | 23 35 i | 30 | 20
Sameer 19 | 31-| 25 | 25 29 eee ay LEY one
9.55 90 | 30 | 34 | 16 37 13 | 29 | 21
10.30 epee) 34 | 16 20 30 | 26 | 24
ee Ts. | ws-| 105 | 150 | 100 | 146 | 104
Total ... | 622 | 378 | 628 | 372 | 630 | 370 | 599 | 401

It may be said that perhaps in the previous
experiments the red and blue were too dark. I
therefore took a very pale solution, and counted the
number twenty times for the red and ten for the blue,

228 EVIDENCE THAT DAPHNIAS —

placing the yellow in another trough, as before, for
comparison. The preference for the yellow was as
marked as ever. In the experiments with the red and
yellow the numbers were respectively

Trove 1. TROUGH 2.
a a
Under the In the Under the In the
yellow. uncovered half. red. uncovered half.
670 330 498 002

When, therefore, the red solution was sufficiently
light, the Daphnias were indifferent to it. In the
experiments with heht blue the numbers were—

TROUGH 1. TROUGH 2. TROUGH 3.
eS ee eee
Under In the Under In the Under In the
the uncovered the uncovered the porcelean uncovered
yellow. halt. blue. half, plate. half.
687 313 286 714 336 664

One other possible objection also suggested itself to
me. I thought it might be said that the Daphnias
went under the yellow and the green not on account of
any preference for yellow or green light, but on account
of the shelter afforded by the covering. To test this,
I covered one half of a trough over with transparent
glass, leaving the other uncovered; but after twenty
observations I found the number of Daphnias in each
half to be practically identical. The mere fact of the
covering, therefore, made no difference. In this way I
was able to test the preference of the Daphnias for
various colours, and the result made it abundantly clear
that Daplinias have the power cf distinguishing between
light of different wave-lengths, and that they prefer
the light which we call yellow and green. Whether it
autually appears to them as it dces to us is, of course,

1
~) oii e:

ss.

— ase

———S Te ee eS ee ee

PERCEIVE DIFFERENCES OF COLOR. 229

another and a more difficult question—one, moreover,
not yet solved even for the higher animals. Nor would
I necessarily claim for them any esthetic sense of
beauty; it must be remembered that they feed on
minute alge and other minute vegetables, the prevalent
colors of which are yellow, yellowish green, and green.
There is, therefore, nothing improbable, @ priorz, but
rather the reverse, in their preference for these colors.

It will be observed that though in these vessels the
Daphnias made their preference unmistakable, there
were always a certain number in the least popular
part. This is natural, because, as the position of the
light half was reversed every observation, the Daphnias
had to swim across the vessel, and some naturally did
not find their way to the favourite part. Then, again,
in any considerable numbers of Daphnias some are
changing, or have recently changed, their skin, and
are, therefore, more or less inactive. Moreover, in pure
water the desire for food must often overpower any
preference for one colour over another. To such causes
as these we must, I think, attribute the presence of so
many Daphnias in the first vessel at the opaque end, and
in the second in the uncovered part.

Still, it was of course not impossible that the pre-
sence, for instance, of a certain number under the red
and blue was due to a difference of taste; that, though
the majority preferred yellow, there might be some
preferring blue or red. ‘To test this I tried the follow-
ing experiment. I placed, as before, fifty Daphnias in
three of the vessels, covering one half of one with the
yellow, of a second with blue, and the third with red.
I then from time to time, at intervals of not less than
half an hour, removed these which were in the un-

230 EVIDENCE THAT DAPHNIAS

covered part and replaced them with an equal number
of fresh ones. If, then, some Daphnias preferred red or
blue, I ought thus to eliminate the others, and gradually
to get together fifty agreeing in this taste. This, how-
ever, was not the case. In the first experiment, an hour
after the Daphnias were placed in the vessels there
were, out of 50, 41 under the yellow, 16 under the red,
and 15 under the blue, the remaining 9, 34, and 39
respectively being in the uncovered portions. ‘These,
then, | removed and replaced by others. After domg
this five times, and thus adding 80 in the yeliow division,
187 in the red, and 209 in the blue, the numbers were 37
under the yellow, 15 under the red, and 6 under the blue.

In the second experiment, the numbers aiter the
first hour were 32 under the yellow, 10 under the red,
and 11 under the blue. Aft-r five observations, during
which 86 were added to the yellow division, 188 to the
red, and 180 to the blue, the numbers were—under the
yellow, 35; red, 11; blue, 15.

In the third experiment, the numbers after half an
hour were 40 under the yellow, 14 under the red, and 8
under the blue. After five observations, during which
73 were added to the yellow, 186 to the red, and 206
to the blue, there were—under the yellow, 45; under
the red, 15; and under the blue, 7.

In the fourth experiment, the numbers after half an
hour were 88 under the yellow, 15 under the red, and
14 under the blue. After six observations, during
which 89 were added to the yellow, 166 to the red, and
176 to the blue, the numbers were—under the yellow,
30; under the red, 19; and under the blue, 10.

In the fifth experiment, the numbers after half an
hour were 40 under the yellow, 14 under the red, and

PERCEIVE DIFFERENCES OF COLOR. 231

13 under the blue. After seven observations, during
which 86 were added to the yellow, 263 to the red, and
272 to the blue, the numbers were—under the yellow,
88; under the red, 13; and under the blue, 19.

Yellow. Red. Blue.
First observation.
At the beginning ... seaut aul 16 15
= end es tite ad i 6
Second observation.
At the beginning... cae eee 10 11
» end pa svar a0 11 15
Third observation.
At the beginning ... xa, AO) 14 8
ao ene. eas eg =: 15 7
Fourth observation.
At the beginning __... az} OO 15 14
See iG | sina aad wea 19 10
Fifth observation.
At the beginning ... ee 14 13
» end ack oo. ae iS 15

I conclude, then, that the presence of some of tlie
Daphnias in the red, blue, and violet is more or less due
to the causes above indicated, and not to any individual
preference for those colors.

My experiments, I think, show that, while the Daph-
nias prefer light to darkness, there is a certain maxi-
mum of brilkiansy beyond which the lht becomes
inconveniently bright to them, and that they can
distineuish cus light of different wave-lengths.
I suppose it would be impossible to prove that they
actually perceive colours; but to sugg+st that the rays
of various wave-lengths produce on their eyes a different
impression from that of cvlor, is te propose an entirely
novel hypothesis.

At any rate, I think I have shown that they do
distinguish between rays of different wave-lengths, and

prefer those which to our eyes appear green and yellow.
12

CHAPTER XI,

ON RECOGNITION AMONG ANTS,

Durine the many years that I have had ants under
observation, I have never on any occasion seen any-
thing like a quarrel between any two ants belonging
to the same community. This is certainly very much
to their credit. The experience of Huber, Forel,
McCook, and others who have wa‘ched ants, is,
moreover, the same as mine. I have also shown* that
they recognize one another even after a separation of
a year and nine months. |

On the other hand, every community of ants is hostile
to every other. J am not now speaking of ants belong-
ing to diffrent kinds, but of ants belonging to the same
species. Some species, indeed, are more intolerant of
strangers than others; but, as regards most species of
ants, it may be said that if an individual be taken from
its own nest and introduced into another, even though
belonging to the same species, it will be at once attacked
and driven, or rather dragged, out.

‘These facts, then, show that the ants of a community
all recognize one another. But when we consider the
immense number of ants in a nest, amounting in some
cases to over 500,000, this is indeed a wonderful fact.

* See “ Ants, Bees, and Wasps.”

oP) & tee haat

eee re ee ee eS ee

we eee

Re OP ae ae ee ey ee ae ee eT PORTS

EXPERIMENTS WITH INTOXICATED ANTS. 239

Tt may be remembered that my nests have enable‘
me to keep ants under observation for long periods, and
that I have thus identified workers-of Lastus niger and
Formica fusca which were at least seven years old, but
my oldest ants have been two queens of Formica fusca,
which I took in a nest in December, 1874. ‘ihey must
then have been nine months old, and of course may
have been more. One of these queens, after ailing
for some days, died on July 30, 1887. She mu-t
then have been more than thirteen years old. I was
at first afraid that the other one might be affected by
the death of her companion. She is, however, still
alive (May, 1888), and, though a little stiff in the
joints, as far as I can judge, in her usual health.
Still, there are only a few queens in a nest, and no
doubt the majority of the workers, at least in the
summer and when the community is most active, are
very young, which adds greatly to the difficulty of sup-
posing that they are personally known to one another.

It has been suggested that each nest has, perhaps,
a special s'gnal or pass-word. T'o test this I took, as I
have already mentioned in my book on “ Ants, Bees, and
Wasps,” a number of ants, half from one nest and half
from another, and made them very drunk, so as to be
thoroughly insensible. Ithen marked them with spots
of diferent colours, so as to distinguish the two lots,
and put them on a table near where some ants belonging
to the nest from which one half of them had been
taken, were feeding on some honey. The table was
surrounded by a moat containing water to prevent the
ants from wandering away. The sober ants were rather
puzzled; but,after examining the intoxicated individuals,
they picked up the strangers and threw them into the

234 EVIDENCE AGAINST THE

ditch, while they carried their own friends into the
nest, where no doubt they slept off the effects of the
spirits. This experiment seemed to show that the
recognition was not effected by means of any sign;
but I thought the suggestion might be tested in
another way.

I made, therefore, the following experiment. I took a
few specimens of Formica fusca trom two different nests,
which I will call A and B, and placed them together.
At first they were rather shy; but after a while they
fraternized. After they had lived amicably together
for three months, | put two of these ants from nest A
into nest B; but they were soon attacked vigorously
and driven out of the nest. I thought it desirable to
repeat and extend this test. Accordingly, on June
16 I put three specimens of F. fusca from my nest
No. 81 with the same number from nest No. 71. ‘Then
on September 19, one of the six having died in the
interval, | put the two from nest 81 into nest 71, and
the three from nest 71 mto 81. They were all attacked,
though not very quickly or vigorously, but eventually all
five were expelled. |

Again, on September 25 I took three ants from each
of these nests and put the six together. Then on
March 19 followmg (one having ated), I put the
two from 71 into 81, and the three from 81 into 71.
They were all attacked, so that they were evidently
recognized as strangers ; but 1t seemed to me that the
attack was less vigorous, and I could not be stre that
they were either killed or driven out. In the course of
the week three or four dead ants were brought out of
each of the nests; but I could not feel certain that
they were tlose eepceuaegead with,

POSSESSION OF A SIGN OR PASSWORD. Pare)

Lastly, on April 9 I again put twelve ants, six
from each of these nests, together, and kept them so
till October. J then took four of those from 71,
put three into 81 and the fourth into 71. [ also took
four of those from 81, and put three into 71, and
the fourth back into 81 among her old friends. The
two ants thus restored respectively to their old nests
were as usual recognized as friends and left quite
unmolested. As regards the other six, the results were
as follows. The ants were introduced into the nests at

8.15 a.m.

Nest 71. Nest 81.
8.45. One was being attacked. One was being attacked.
9.15. None were os 9 9
9.45. Two were » 3 3
10.15. One was “, > 2
10.45. None were = 59 9
12.30. Two were 5 99 39
1.30. Two were s None were 5,
2.30. One was 9 9 oP)

I do not give these results as by any means proving
that ants do not recognize their friends by means of
smell. They do seem, however, at any rate, to show that
not even six months of close companionship under pre-
cisely similar conditions will so far assimilate the odour
as tolead to confusion. If the recognition 7s due in any
degree to this cause, the odour is therefore probably an
hereditary characteristic.

In the interesting memoir already cited, Forel says,*
“Lubbock (loc. cit.) a cru démontrer que les fourmis
enlevées de leur nid a l’état de nymphe et écloses hors
de chez elles étaient néanmoins reconnues par leurs

* Recueil Zool. Suisse, 1887.

236 EXPERIMENTS WITH ANTS REMOVED FROM THE

compagnes lorsqu’on les leur rendait. Dans mes
Fourmis de la Suisse, avais cru démontrer le coutraire.
Voici une expérience que j’ai faite ces jours-ci: Le 7
aout, je donne des nymphes de Formica pratensis pres
d’éclore a quelques Formica sanguinea dans une boite.
Le 9 aott quelques-unes éclosent. Le 11 aott, au
matin, je prends l’une de jeunes pratensis agée de deux
ou trois jours seulement et je la porte a sa fourmiliere
natale dont elle était sortie comme nymphe seulement
4 jours auparavant. Elle y est fort mal recue. Ses
nourrices dil y a 4 jours lempoignent qui par la téte,
qui par le thorax, qui par les pattes en recourbant leur
abdomen d’un air menacant. Deux d’entre elles la
tinrent longtemps en sens inverse chacune par une
patte en l’écartelant. EEnfin cependant on fimit par la
tolérer, comme on le fait aussi pour de si jeunes fourmis
(encore blanc jaunatre) provenant de fourmiliéres dif-
férentes. J’attends encore deux jours pour laisser durcir
un peu mes nouvelles écloses. Puis j’en reporte deux
sur leur nid. Elles sont violemment attaquées. L’une
(elles est inondée de venin, tiraillée et tuée. L’autre
est longtemps tiraillée et mordue, mais finalement
laissée tranquille (tolérée?). On m/’objectera l’odeur
des sanguinea qui avait vécu 4 jours avec la premiere
et 6 jours avec les deux dernieres. A cela je répondrai
simplement par l’expérience de la page 278 a 282 de
mes Fournus de la Suisse, ot des F. pratensis adultes
séparées depuis deux mois de leurs compagnes par une
alliance forcée avec des F’. sanguinea, alliance que j’avais
provoquée, reconnurent immédiatement leurs anciennes
compagnes et s'allierent presque sans dispute avec elles.
Je maintiens done mon opinion: les fourmis apprenneit
4 se connaitre petit A petit a partir de leur éclosion.

NEST AS PUP AND SUBSEQUENTLY RESTORED. 237

Je crois du reste que c’est au moyen de perceptions
olfactives de contact.” *

I have, however, repeated my previous observations,
with the same results.

At the beginning of August I brought in a nest of
Lasius niger containing a large number of pupe.
Some of these I placed by themselves, in charge of three
ants belonging to the same species, but taken from a
nest I have had under observation for rather more than
ten years. On August 28 I tovk twelve of the young
ants, which in the mean time had emerged from the sepa-
rated pups, selecting some which had almost acquired
their full colour. Four of them I placed in their old
nest, and four in that from which their nurses were taken.

At 4.30 in their own nest none were attacked.

= ieee as nurses’ nest one was attacked.

= 9.0 ie own nest none were attacked. .
ee se as nurses’ nest all four were attacked.
ag SO - own nest none were attacked.

ae 3 nurses’ nest three were attacked.

The next day I took six more and marked them
with a spot of paint as usual, and at 7.30 ponriced
them in their own nest.

At 8.0 I found 5 quite at home; the others I could not see, but none
were attacked.

”9 8.30 9 +) 49 39 39 9
” 9.0 ” 3 9 93 39 39
” 10.0 99 4 39 19 39 F)
” 11.0 99 4) Pp) oP) 39 39
” 12.0 eH 3 9 9 3 oh)
” 1.0 39 3 2° 2 9 39
9 4.0 93 4 9 »P) 39 39
” 7.0 9 1 ” 9 9 99
” 9.0 9 2 9 39 9 39

* “Forel. Exp. et Rem. crit. sur les Sensations des Insectes,”
Recueil Zool. Suisse., 1887.

238 EXPERIMENTS WITH DROWNED ANTS.

The next morning I could only see two, but none
were being attacked, and there were no dead ones. It
is probable that the paint had been cleaned off the
others, but it was not easy to find them all among so
many. At any rate, none were being attacked, nor had
any been killed.

These observations, therefure, quite confirm those
previously made, and seem to show that if pupe are
taken from a nest, kept till they become perfect insects,
and then replaced in the nest, they are recognized as
friends.

As regards the mode of recognition, Mr. Me Cook
considers that it is by scent, and states that if ants are
more or less soaked in water, they are no longer recog-
nized by their friends, but are attacked. He mentions
a case in which an ant fell accidentally into some
water: “She remained in the liquid several moments,
and crept out of it. Immediately she was seized ina
hostile manner, first by one, and then another, then by
a third, the two antenne and one leg were thus held.
A fourth one assaulted the middle thorax and petiole.
The poor little bather was thus dragged helplessly to
and fro for a long time, and was evidently ordained to
death. Presently I took up the struggling heap. Two
of the assailants kept their hold, one finally dropped ;
the other I could not tear loose, and so put the pair
back upon the tree, leaving the doomed immersionist
to her hard fate.”

His attention having been called to this, he noticed
several other cases, always with t'e same result. I
have not myself been able to repeat the observation
with the same species, but with two at least of our
native ants the results were exactly reversed. In one

RECOGNITION AFTER A YEAR AND NINE MONTHS. 239

case five specimens of Lasius niger fell into water and
remained immersed for three hours. I then took them
out and put them into a bottle to recover themselves.
The following morning I allowed them to return.
They were received as friends, and, though we watched
them from 7.30 till 1.80 every hour, there was not the
slightest sign of hostility. The nest was, moreover,
placed in a closed box, so that if any ant were killed
we could inevitably find the body, and no ant died.
In this case, therefore, it is clear that the immersion
did not prevent them from being recognized. Again,
three specimens of Formica fusca dropped into water.
After three hours I took them out, and, after keeping
them by themselves for the night to recover, I put
them back into the nest. ‘They were unquestionably
received as friends, without the slightest sign of
hostility or even of doubt. I do not, however, by any
means intend to express the opinion that smell is not
the mode by which recognition 1s effected.

It will be remembered, perhaps, that my ants (For-
mica fusca) recognized one another after a separation
of a year and nine months, though “after some months’
separation they were occasionally attacked, as some of
the ants, perhaps the young ones, did not recognize
them. Still, they were never killed or driven out of
the nest, so that evidently when a mistake was made
it was soon discovered.” Hence it would appear that
there are differences in the memory of. different
species. |

In one case Forel had taken some ants from a
large nest of Componotus, for the experiments on
their sensibility to the ultra-violet rays, to which I
have already referred. After his observations were

240 SUPPOSED RECOGNITION BY SCENT.

concluded, he returned them to the nest, some after
eight, some after forty-one days. ‘Those which were
returned after eight days were at once recognized,
while as regards those which had been forty-one days
away from home. “Qn reeulait de part et d’autre, se
menagait des mandibules, s’examinait a fond avec les
antennes, se mordait méme. fPlusieurs méme allérent
dans leur irritation jusqu’ a essayer de décapiter et
méme a décapiter quelques-unes de leurs anciennes
compagnes et sceurs avec leurs mandibules (c’est le
mode de combat des Camponotus)! Les fourmis vernies
prirent part a ces rixes aussi bien que les non vernies;
je les vis méme attaquer, et elles étaient a peine
moins adroites. Les combats ne cessérent entiérement
qu’au bout d’un ou deux jours, et, a part les quelques
victimes du premier jour, l’incident se termina par une
alliance.”

Forel seems to entertain no doubt that the recog-
nition is effected by a form of smell, which he terms
“odorat au contact.” He says, “ Beaucoup d’insectes
ont en outre une sorte d’odorat au contact que nous ne
possédons pas et qui permet entre autres aux fourmis
de distinguer leurs compagnes de leurs ennemies.”

His observations, however, do not favour the hy-
pothesis that the recognition may be by smell. If
the ants recognized their companions by avy odour
characteristic of the community, the lapse of thirty
days could not have made any difference. Here the
question of memory would not enter, because the per-
ception of the odour would in both cases be continuaily
before them. M. Forel is so excellent an ob-zerver,
and has so great a knowledge of the ways of ants,
that his opinion is entitled to great weight. It

RECOGNITION BY MEANS OF THE ANTENNE. 241

would be very interesting to repeat similar observations,
for if it turn out to be the case that separations of
comparatively few days lead, in some species, to a
want of recognition, it would be a strong argument
against the hypothesis that this recognition is due to
smell. |

It certainly seems as if the recognition was effected
to a great extent by the antenne. Not only do the
ants cross and recross them, almost, so to say, as two
deaf mutes conversing by their fingers ; but, as M. Forel
has shown, if ants of different species are brought
together after the removal of their antenne they show
no signs of hostility. That this latter statement is
correct I am quite content to take on M. Forel’s
authority ; but it is not so conclusive as might seem
at first sight, because in ants, as in men, “a fellow-
feeling makes us wondrous kind,” and ants when
isolated, and especially when suffering, are much less
pugnacious than they are under normal conditions.

CHAPTER XII.
ON THE INSTINCTS OF SOLITARY WASPS AND BEES.

THE hive bee and the common wasps are so familiar
and so interesting that they have to a great extent
diverted attention from the so-called solitary species
of the same groups. ew, for instance, are aware that
about 4500 species of wild bees are known, and of
wasps 1100, of which some 170 and 16 respectively
live in Britain.

These insects often live in association, but do not
form true communities. Speaking generally, we may
say that each female constructs a cell, every species
having its own favourite site, sometimes underground,
sometimes in a hollow stick, in an empty snail-shell,
or built against a wall, a stone, or the branch of a tree.
Having completed her cell, the female stores up in it
a sufficient supply of food, which in the case of bees
consists of pollen and honey; while the wasps select
small animals, such as beetles, caterpillars, spiders, ete.,
each species generally having one kind of prey. The
mother then Jays an egg, after which she closes up
the cell, and commences another. Having thus pro-
vided sufficiently for her offspring, she generally takes
no further heed of it. This is not, however, an invari-
able rule: in the genus Bembex, for instance, the

INSTINCT OF RENDERING VICTIMS INSENSIBLE. 2438

mother, instead of provisioning her cell once for all,
brings food to the young grub from day to day.

This, however, is an exceptional case, and the mode
of life of the solitary wasps raises one of the most
interesting questions in connection with instinct. The
Ammophila, for instance, having built her cell, places
in it,as food for her young, the full-grown caterpillar of
a moth, Noctua segetum. Now, if the caterpillar were un-
injured, it would strnggle to escape and almost inevit-
ably destroy the egg; nor would it permit itself to be
eaten. On the other hand, if it were killed, it would
decay and soon become unfit for food. The wasp, however,
avoids both horns of this dilemma. Having found her
prey, she pierces with her sting the membrane between
the head and the first segment of the body, thus nearly
disabling the caterpillar, and then proceeds to inflict
eight more wounds between the following segments ;
lastly crushing the head, and thus completely paralyzing
her victim, but not actually killmg it; so that it hes
helpless and motionless, but, though living, let us
hope insensible. M. Fabre, to whom we are indebted
for a most interesting and entertaining series of essays
on this group of insects, argues that this remarkable
instinct cannot have been gradually acquired.

The spots selected are, he says, exactly those
occupied by the ganglia. No others among the in-
numerable points which might have been chosen would
have answered the purpose; not one wound is mis-
placed or without effect. M. Fabre truly observes that
chance offers no explanation.* Moreover, he unhesi-

* In the case of other insects, such as Mutilla, Chrysis, Leucospis,
Anthrax, etc., which do not possess the instinct of paralyzing their
victims, the young feed on the chrysalis, which is normally without
power of movement.

244 ORIGIN OF INSTINCTS.

tatingly asserts that ‘Si de son cété l’hyménoptére
excelle dans son art, c'est qu il est fait pour lexercer ;
c'est qu'il est doué, non seulement d'outils, mais encore
de la maniére de s’en servir. Et ce don est originel,
parfait dés le début; le passé n’y a rien ajouté, l’avenir
n’y ajoutera rien.”* But how was it acquired? M.
Fabre cuts the Gordian knot. “ Et tout naivement je
me dis: Puisqu’il faut des Araignées aux Pompiles, de
tout temps ceux-ci ont possédé leur patiente astuce et
les autres leur sotte audace. C’est puéril, si l’on veut,
peu conforme aux visées transcendantes des théories a
la mode; il n’y a la ni objectif ni subjectif, ni adapta-
tion ni différentiation, ni attavisme ni transformisme ;
soit, mais du moins je comprends.” 3

“Je comprends!” M. Fabre says he understands,
and no doubt he thinks so; but I confess that his
explanation seems to me to leave us just where we
were. ‘To my mind, I confess, it seems to me to throw
no light whatever on the matter. M. Fabre asserts
that the habits of these insects have been “de tout
temps” exactly what they are now. I pass by the fact
that the Hymenoptera are, geologically speaking, of
comparatively recent appearance. But is it the case
that habits are so invariable? Quite the reverse. The
cases of variation are innumerable. )

Romanesf refers to a criticism of the same nature
by hirby and Spence. “Why,” they ask, “if instincts
are open to modification by experience and intelligence,
are not bees sometimes found to use mud or mortar
instead of wax or propolis? Show us,” they say, “ but
one instance of their having substituted mud for

* J. H. Fabre, “ Nouveaux Souvenirs Entomologiques.”
“ Mental Evolution in Animals.”

HABITS NOT INVARIABLE. 245

propolis, ... and there could be no doubt of their
having been guided by reason.” Such cases have. how-
ever, been observed. Andrew Knight found that his
bees collected some wax and turpentine with which he
had covered some decorticated trees, and used it instead
of propolis, the manufacture of which they discontinued.
Nay, M. Fabre has himself placed on record some cases
of the same kind, and shown that the instincts of these
enimals are not absolutely unalterable. Thus one
solitary wasp, Sphex flavipennis, which provisions its nest
with small grasshoppers, when it returns to the cell,
leaves the victim outside, and goes down for a moment
to see that all is night. During her absence M. Fabre
moved the grasshopper a little. Out came the Sphex,
soon found her victim, dragged it to the mouth of the
cell, and left it as before. Again and again M. Fabre
moved the grasshopper, but every time the Sphex did
exa'tly the same thing, until M. Fabre was tired out.
All the insects of this colony had the same curious
halit; but on trying the same experiment with a
Sphex of the following year, after two or three dis-
appointments she learned wisdom by experience, and
earried the grasshopper directly down into the cell.

- Humenes pomiformis builds, as already mentioned,
a cell in the open air. If attached to a bread base,
“Crest un déme avec goulot central, évasé en embou-
chure d’urne. Mais quand l’appui se réduit a un point,
sur un rameau d’arbuste par exemple, le nid devient
une capsule sphérique, surmontée toujours d’un goulor,
bien entendu.” *

Again, he has shown good reason for believing
that, although the Tachytes nigra generally makes its

*~ Loc e2t., p. 66.

246 CHANGE OF INSTINCTS—BEMBEX.

own burrow and stores it with paralyzed prey for its
own larvee to feed on, yet that, when this insect finds a
burrow already made and stored by another Sphex, it —
takes advantage of the prize, and becomes for the
occasion parasitic. On which Mr. Darwin has justly
observed that he could see no difficulty in natural
selection making an occasional habit permanent, if of
advantage to the species, and if the insect whose nest
and stored food are thus feloniously appropriated be
not thus exterminated.

The problem is certainly one of great difficulty, and
it is with diffidence that I would suggest to M. Fabre
certain considerations which may perhaps throw some
light on it. Let us examine some of the other solitary
wasps, and see whether their habits afford us any clue.
That an animal of prey knows where its victim is
most vulnerable, has not in itself anything unusual or
unaccountable.

The genus Bembex kills the insects on which its
young are fed, and supplies the cell with a fresh
victim from time to time. Humenes, like Ammophila
and Sphex, stores up the victims once for all. They
are grievously wounded, but not altogether paralyzed.
Here, then, we have the very condition which M. Fabre
considers would be fatal to the tender egg of the wasp.
But not necessarily so. The wretched caterpillars le
ina wriggling mass at the bittom of the cell; a clear
space is left above them, and from the summit of the
cell the delicate egg is suspended by a fine thread, so
that, even if touched by a caterpillar in one of its con-
vulsive struggles, it would simply swing away in safety.
When the young grub is hatched, it suspends itself to
this thread by a silken sheath, in which it hangs head

ODYNERUS—AMMOPHILA. 247

downwards over its victims. Does one of them struggle ?
quick as lightning it retreats up the sheath out of
harm’s way.

In Odynerus the arrangement is very similar, but
the grub simply attaches itself to the support, and
does not construct a tube. Moreover, while in the
solitary bees and wasps the laying of the egg is generally
the final operation before the closing of the cell, in
Odynerus, on the contrary, or at least in Odynerus
renifornus, the egg is laid before the food is provided.
This, perhaps, may have reference to the different con-
dition of the victims.

According to Marchal,* Cerceris ornata practically
kills her victim ; moreover, she stings it not in, but
between, the ganglia, and though the first sting is
planted between the head and thorax, the following
ones do not always follow the same order.

At present the Ammophila supplies each cell with
one large caterpillar; but was this always so? One
species of Odynerus deposits in each cell no less than
twenty-four victims, another only eight. Humenes
Amedet regulates the number according to the sex:
ten for the female grub, five only for the smaller male.

Moreover, while phytophagous larve will not gene-
rally eat any plants but those to which they are
accustomed, it has been proved that, as a matter of
fact, these larvee will feed and thrive on other insects
almost, if not quite, as well as on their natural food.

Is it, then, impossible that in far bygone ages the
larvee may have grown more rapidly, so that the
victims had not time to decay; or that the ancestors

* Marchal, “Sur Instinct du Cerceris ornata,” Arch. d. Zool. Exper.,
1887.

248 MODIFIABILITY OF INSTINCTS.

of our present Ammophilas may have fed their young
from day to day with fresh food, as Bembex does even
now; that they may then have gradually brought the
provisions at longer intervals, choosing small and
weak victims, and laying the ege in a special part of
the cell, as Eumenes does? that during these long
ages they may have gradualiy learnt the spots where
their sting would be most effective, and, thus saving
themselves the trouble of capturing a number ot
viciims, have found that it involved less labour to select
a fine fat common caterpillar, such as that of Noctua
segetum, and so have gradually acquired their present
habits? Wonderful doubtless they are; but, though
I hint the suggestion with all deference, such a
sequence does not seem to me to present any in-
superable difficulty.

This suggestion was made in the Contemporary
Review for 1885, and I was much interested to find in
Mr. Darwin’s life that he had made a similar suggestion
in a letter to M. Fabre. He refers to the great skill
of the Gauchos in killing cattle, and suggests that each
young Gaucho sees how the others do it, and with a
very little practice learns the art. “I suppose that
the sand-wasps originally merely killed their prey by
stinging them in many places (see p. 129 of Fabre’s
‘Souvenirs, and p. 241), and that to sting a certain
segment was found by far the most successful method,
and was inherited like the tendency of a bulldog to pin
the nose of a bull, or of a ferret to bite the cerebellum.
It would not be a very great step in advance to prick
the ganglion of its prey only slightly, and thus to give
its larvee fresh meat instead of only dried meat.” *

* “Tife and Letters of Charles Darwin.”

DIFFERENCES UNDER DIFFERENT CIRCUMSTANCES. 249

Perhaps, however, it may be asked, Why should the
insect change its habits? Several reasons might be sug-
gested. ‘The prey first selected might be exterminated,
or at any rate diminish in numbers, and, though each
species as a general rule confines itself to one special
victim, some exceptions have already been noticed.
For instance, Sphex flavipennis habitually preys on a
species of grasshopper, but on the banks of the Rhone
M. Fabre found it, on the contrary, attacking a field
cricket, whether from the absence of the grasshopper or
not he was unable to determine.

Take another case. M. Fabre denies* that the
different species of Sphex can ever have been derived
from one source. Lvery species now, he observes, bas
some one victim, some one insect on which it preys, to
which it restricts itself, and which the other species do
not attack. but “Que chassait, je vous prie, ce proto-
type des Sphégiens? Avait il régime varié ou régime
uniforme? Ne pouvant décider, examinons les deux
cas.”

He begins by supposing that with the ancestor of the
Sphex, “ Le régime était varié. J’en félicite hautement
ce premier né des Sphex. II était dans ies meilleures
conditions pour laisser descendance prospere.” Is it
likely then, he says, that they would have limited
themselves to one prey, and thus have foolishly
diminished their chances in life? “ Mais non,” he adds,
in his lively style, “mes beaux Sphex, vous n’avez pas
été aussi idiots que cela. Sivous étesde nos jours can-
tonnés chacun dans un mets de famille, c’est que votre
ancétre ne vous a pas enseigné la variété.”’

He then discusses the alternative whether the

* “ Souv. Entem., troisi¢me série.”

250 ORIGIN OF THE HABITS. OF SPHEX.

ancestral Sphex restricted itself to one victim, and
that its descendants “subdivisés en groupes et con-
stitués enfin en autant d’especes distinctes par le lent
travail des siécles, se sont avisés qu’en dehors du
comestible des ancétres il y avait une foule dautres
aliments.”

This, he says, supposes that they experimented on
various victims, found several of them to their liking,
and then, after a period of varied and plentiful diet,
voluntarily abandoned so great an advantage.

“Avoir découvert, par vos essais d’age en age, la
variété de Valimentation ; l’avoir pratiquée, au grand
avantage de votre race, et finir par Puniformité, cause
de décadence ; avoir connu l'excellent et le répudier
pour le médiocre, ‘Oh! mes Sphex, ce serait stupide si
le transformisme ayait raison.’ ”

“ Jestime,” then he concludes, “que votre ancétre
commun, votre précurseur, a gotits simples ou bien @
gotts multiples, est une pure chimére.”

No doubt the habits of Hymenoptera present many
difficulties, and have undoubtedly many surprises in
store for us, and I cannot think the matter is so clear
as M. Fabre imagines, or that he has exhausted the
possible cases. It is possible, though it is, [ admit,
only a supposition, that the ancestral Sphex hunted
some species which does not now exist—at least not in
the south of France—and which might have disappeared
gradually. As it became rarer, they might be driven
to attack other prey, and M. Fabre has himself shown
by a variety of most ingenious experiments that the
larvee are by no means fastidious as to their food. The
Hymenoptera vary considerably in size, and the larger
individuals might be able to overmaster some large

RACE DIFFERENCES. 251

insect, while the feebler specimens were compelled to
content themselves with humbler fare.

This is no purely imaginary case. M. Fabre himself
distinguishes three races—or are they species ?—ot Leu-
cospis which live on the three species of Chalicodomas.

« Venu du Chalicodome des galets ou des murailles,
dont l’opulente larve le sature de nourriture, il mérite
par sa grosseur le nom le Leucospis gigas, que lui
donne Fabricius; venu du Chalicodome des hangars, 1
ne mérite plus que le nom de Leucospis grandis, que
lui octroie Klug. Avec une ration moindre, le géant
baisse d’un degré et n'est plus que le grand. Venu
du Chalicodome des arbustes, il baisse encore, et si
quelque nomenclateur s’avisait de le qualifier, il
naurait plus droit qu’au titre de médiocre.

The Anthrax, again, differs considerably a-cording to
the species on which it has fed, those coming from the
cocoons of Osmua tricorms being much larger from
those from O. cyanea.

Or it might well happen that while the victim was
from some cause or other, say for instance the absence
of food elsewhere, limited to a particular district, the
region beyond was suited to the ancestress Sphex. In

that case, would she not naturally try whether she

could not find some other suitable food? Tuis again, is
not a purely imaginary case. M. Fabre himself tells us
that while “ la Scolie interrompue avait pour gibier aux
environs d’Avignon, la larve de l’Anoxie velne (Anozia
villosa). Aux environs de Sérignan, dans un sol sablon-
neux semblable, sans autre végétation que quelques
maigres gramens, je lui trouve pour vivres |’Anoxie
matutinale (Anoxia matutinalis), qui remplace ici la
velue.”

252 POWER OF DETERMINING SEX.

That bees soon take to newly introduced flowers is a
familiar case which every one must have noticed, and
which it is surely not logical to dismiss by the conve-
nient process of referring it to “instinct.” It is indeed
difficult for any one who watches these insects to deny
to bees the possession of a higher and conscious faculty.

In considering the question whether these remarkable
instincts were originally, so to say, engrafted in the
inseet, or whether they were the resu!t of innumerable
repetitions of similar actions carried on by a long
series of ancestors, we may perhaps be aided by the
consideration that, though the results would in either
case be in many respects the same, there are some in
which they would altogether differ. In the former, for
instance, we might expect that the insect would be so
gifted that uo slight obstacle should interfere with the
great end in view: in the latter, on the contrary, the
very repetition which gave such remarkable results
would tend to incapacitate the insect from dealing with
any unusual conditions.

LIMITATION OF INSTINCT.

We should, in fact, find side by side with these won-
derful instincts almost equally surprising evidence of
stupidity. Now, one species of Sphex preys on a large
grasshopper (Ephippigera). Having disabled her vic-
tim, she drags it along by one of the antenne, and
M. Fabre found that if the antenne be cut off close to
the head, the Sphex, after trying in vain to get a grip,
cives the matter up as a bad job, and leaves her victim
in despair, without ever think ng of dragging it by one
of its legs. Again, when a Sphex had provisioned her
cell, laid her egg, and was about to c’ose it up, M.

LIMITATION OF INSTINCT. 253

Fabre drove her away, and took out both the Ephippi-
gera and the egg. He then allowed the Sphex to return.
She went down into the empty cell, and though she
must have known that the grasshopper and the egg
were no longer there, yet she proceeded calmly to stop
up the orifice just as if nothing had happened.

The genus Sphex paralyzes its victims and provisions
its cell once for all. Bembex, on the contrary, as
already mentioned, kills the insects on which its young
are to feed, and, perhaps on this account, brings its
young fresh food (mainly flies) from time to time.
But while the Bembex thus preys on some flies, there
are others which avenge their order. The genus
Miltogramma lays its eggs in the cell of the Bembex ;
and, though there seems no reason why the Bembex,
which is by far tle stronger msect, should tolerate this
intrusion, which, moreover, sbe shows unmistakably to
be most unpalatable, she never makes any attack on
her enemy. Nay, when the young of the Miltogramma
are hatched, so far from being killed or removed, these
entomological cuckoos are actually fed until they reach
maturity. Nevertheless, it seems contrary to etiquette
for the fly to enter the cell of the Bembex ; she watches
the opportunity when the latter is in the cell and is
drageing down the victim. ‘Then is the Miltogramma’s
opportunity; she pounces on the victim, and almost
instantaneously lays on it two or three eggs, which are
then transferred, with the insect on which they are to
feed, to the cell.

It is remarkable how the bembex remembers (if one
may use such a word) the entrance to her cell, covered
as it is with sand, exactly to our eyes like that all
ronnd. On the other band, M. Fabre found that if he

254 TOLERATION OF PARASITES.

removed the surface of the earth and the passage,
exposing the cell and the larva, the Bembex was quite
at a loss, and did not even recognize her own offspring.
It seems as if she knew the door, the nursery, and the
passage, but not her child.

Another ingenious experiment of M. Fabre’s was
made with a mason bee (Chalicodoma). This genus
constructs an earthen cell, through which at maturity
the young insect eats its way. M. Fabre found that if
he pasted a piece of paper round the cell, the insect had
no difficulty in eating through it; but if he enclosed the
cell in a paper case, so that there was a space even of
enly a few lines between the cell and the paper, in that
case the paper formed an effectual prison. The instinct
of the insect taught it to bite through one enclosure,
but it had not wit enough to do so a second time.

One of the most striking instances of stupidity
(may I say) is mentioned by M. Fabre, in the case of
one of his favourite bees, the Chalicodoma pyrenaica.
This species builds cells of masonry, which she fills with
honey as she goes on, raising the rim a little, then
making a few journeys for honey, then raising the rim
again, and so on until the cell is completed. She then
prepares a last load of mortar, brings it in her mandibles,
lays her egg, and immediately closes up the cell;
having doubtless provided the mortar beforehand, lest
during her absence an enemy should destroy the egg
or any parasitic insect should gain admittance. ‘This
being so, M. Fabre chose a cell which was all but
finished, and during the absence of the bee he broke
away part of the cell-covering. Again, in some half- .
finished cells he broke away a little of the wall. In
all these cases the bee, as might be expected, repaired

CASES OF APPARENT STUPIDITY. 255

the mischief, the operation being in the natural order
of her work. But now comes the curious fact. In
another series of cells M. Fabre pierced a hole in the cell
below the part where the bee was working, and through
which the honey at once began to exude. The poor
stupid little bee, however, never thought of repairing
the breach. She worked on as if nothing had happened.
In her alternate journeys she brought first mortar and
then honey, which, however, ran out again as fast as it
was poured in. This experiment he repeated over and
over again with various modifications in detail, but
always with the same result. It may be suggested that
possibly the bee was unable to stop up a hole once
formed. But that could not have been the case. M.
Fabre took one of the pellets of mortar brought by the
bee, and successfully stopped the hole himself. The
omission, therefore, was due, not to a want of power,
but of intellect. But M. Fabre carried his experiment
still further. Perhaps the bee had not noticed the injury.
He chose, therefore, a cell which was only just begun
and contained very little honey. In this he made a
comparatively large hole. The bee returned with a
supply of honey, and, seeming much surprised to find
the hole in the bottom of the cell, examined it carefully,
felt it with her antenne, and even pushed them through
it. Did she then, as might naturally have been expected,
stopitup? Not a bit. The unexpected catastrophe
transcended the range of her intellect, and she calmly
proceeded to pour into this vessel of the Danaides load
after load of honey, which of course ran out of the bottom
as fast as she poured it in atthe top. All the afternoon
she laboured at this fruitless task, and began again
undiscouraged the next morning. At length, when she
13

256 M. FABRE’S EXPERIMENTS,

had brought the usual complement of honey, she laid
her egg, and gravely sealed up the empty cell. In
another case, he made a large hole in the cell just above
the level of the honey—a hole so large that through it
he was able to see the bee lay her egg. Having doneso,
she carefully closed the top of the cell, but though she -
closely examined the hole in the side, it did not enter
into the range of her ideas that such an accident could
take place, and it never occurred to her to cover it up.
Another curious point raised by these ingenious
experiments has reference to the quantity of honey.
The cell is by no means filled; a space is always left
between the honey and the roof of the cell. The usual
depth of the honey in a completed cell is ten milli-
metres. But the bee is not guided by this measure-
ment, for in the preceding cases she sometimes closed
the cell when the honey had a depth of only five milli-
metres, of three, or even when the cell was almost empty.
No; in some mysterious manner the bee feels when she
has provided as much honey as her ancestress had done
before her, and regards her work as accomplished.
What a wonderful, but what a narrow, nature! She
has built the cell and provided the honey, but there
her instinct stops: if the cell is pierced, if the honey is
removed, it does not occur to her to repair the one or
fill up the other. M. Fabre not unnaturally asks,
“ Avec la moindre lueur rationnelle, l’insecte déposerait-
il son ceuf sur le tiers, sur le dixiéme des vivres réces-
saires ; le déposerait-il dans une cellule vide; laisserait-
il le nourrisson sans nourriture, incroyable aberration de
la maternité? J’ai raconté, que le lecteur décide.”
The family of bees is generally reckoned to be one
of great intelligence, but these and many other similar

LIMITATION OF INSTINCT. 257

instances which might be recorded seem to show great
limitation of intelligence.

Let me give one other, which any person may easily
test for himself. I took a glass shade or jar eighteen
inches long, and with a mouth six and a half inches
wide, turning the closed end to the window, and put in
a common hive bee. She buzzed about for an hour,
when, as there seemed no chance of her getting out,
I put her back into the hive. ‘Two flies, on the
contrary, which I put in with her, got out at once.
Again I put another bee and a fly into the same glass;
the latter flew out at once. For half an hour the
bee tried to get out at the closed end; I then turned
the glass with its open end to the light when she flew
out at once. To make sure, I repeated the experiment
once more, with the same result.

_ And yet there is, no doubt, ample foundation for the
ordinary view which attributes considerable intelligence
to the bee, within the sphere of her own operations.

Several other points of resemblance between
instincts and habits could be pointed out. As in
repeating a well-known song, so in instincts, one action
follows another by a sort of rhythm. If a person be
interrupted in a song, or in repeating anything by rote,
he is often forced to go back to recover the habitual
train of thought; so P. Huber found it was with a
caterpillar, which makes a very complicated hammock;
for if he took a caterpillar which had completed its
hammock up to, say, the sixth stage of construction,
and put it into a hammock completed up only to the
third stage, the caterpillar simply re-performed the
fourth, fifth, and sixth stages of construction. “ If, how-
ever, a caterpillar were taken out of a hammock made

258 INSTINCTS AND HABITS.

up, for instance, to the third stage, and were put into
one finished up to the sixth stage, so that much of its
work was already done for it, far from feeling the
benefit of this, it was much embarrassed, and, in order
to complete its hammock, seemed forced to start from
the third stage, where it had left off, and thus tried to
complete the already finished work.’’*

Another very interesting series of observations which
we owe to M. Fabre has reference to the question of
sex, and it would really seem that the mother can
regulate the sex of the egg at will. In many of our
wild bees, the females are much larger than the males.
The male lives a life of pleasure, idle but short.
“Quinze jours de bombance dans un magasin a miel,
un an de sommeil sous terre, une minute d’amour au
soleil, puis la mort.” :

But the female “C’est la mére, la mére seule qui,
péniblement, creuse sous terre des galeries et des
cellules, pétrit le stue pour enduire les loges, magonne
la demeure de ciment et de graviers, taraude le bois et
subdivise le canal en étages, dé-oupe des rondelles de
feuilles qui seront assemblées en pots a miel, malaxe
la résine cueillie en larmes sur les blessures des pins
pour édifier des votites dans la rampe vide d’un es-
cargot, chasse la proie, la paralyse et la traine au
logis, cueille la poussiere pollinique, élabore le miel
dans son jabot, emmagasine et mixtionne la patée.
Ce rude labeur, si impérieux, si actif, dans lequel se
dépense toute la vie de l’insecte, exige, c’est évident,
une puissance corporelle bien inutile au male, l’amou-
yeux désceuvré.”

In the hive bee the drone cells differ materially 1 in
shape from those of the queens and workers.

* Darwin, “ Origin of Species.”

INFLEXIBILITY OF INSTINCT. 259

In the solitary wasps, where the females are much
larger than the males, the mother builds a larger cell and
provides more food for the former than for the latter.

The Chalicodoma (one of the mason bees) often lays
her eggs in old cells of the previous year. These
are of two sizes—large ones, originally built for the
females, and small ones for the males. Now, in
utilizing old cells, the bee always places male eggs in
male cells and female eggs in female cells. If, how-
ever, a female cell be cut down so as to reduce the
size, then indeed the bee deposits in it a male egg.

The bees belonging to the genus Osmia* arrange
their cells in a row in a hollow stick, or some other
similar situation, and it has long been known that in
these and similar cases the cells first provisioned, and
which are therefore furthest from the entrance, always
contain females, while the outer cells always contain
males.

There is an obvious advantage in this, because the
males come out a fortnight or more before the females,
and it is, of course, convenient that those which have
to come out first should be in the cells nearest the
door. ‘The bee does not, however, lay all the female
eggs first, and then all the male eggs. By no means.
She produces altogether from fifteen to thirty eggs, but
seldom arranges them in one row; generally they are
in several series, and in every one the same sequence
occurs—females further from, and males nearest to, the
door.

For instance, one of M. Fabre’s marked bees—one,
moreover, of exceptional fertility—occupied some glass

* Osmia tridentata constitutes an exception to the general rule in
this respect, as in some others.

260 DIFFERENT HABITS OF MALES AND FEMALES.

tubes, which he arranged conveniently for her. From
the 1st to the 10th of May she constructed, in one tube,
eight cells—first seven female, and then one male.
From the 10th to the 17th, in a second tube, she built
first three female and then three male cells; from the
17th to the 25th, in a third, three female and then
two male; on the 26th, in a fourth, one female; and,
finally, from the 26th to the 30th, in a fifth, two female
and three male: altogether twenty-five, seventeen
female and eight male cells.

The advantage of this is clear, but the manner in
which it is secured is not so obvious. It might be
suggested that the quantity of food was not regulated
by the sex of the young one, but that the sex depended
on the quantity of food. This would be very improb-
able, and M. Fabre attempted to disprove it by some
very ingenious experiments. He found that if he took
some of the food from a female cell, the bee or wasp
produced was still a female, though a starveling; while
if he added food to a male cell, the larva still pro-
duced a male, though a very large and fine one.

M. Fabre then made some of his most ingenious
experiments. He brought into his room a large number
of cocoons of Osmia. When the perfect insects were
about to emerge, he arranged for them a number of
glass tubes, of which the Osmias gladly availed them-
selves, and in which they proceeded to construct their
~ cells. The usual arrangement, as already mentioned,
is that the males are placed nearest to, and the female
furthest from, the door. But M. Fabre so arranged
the tubes that each was in two parts, an outer wider
portion having a diameter of eight to twelve milli-
metres, which is sufficient for a female cell; and an

ARRANGEMENT OF MALE AND FEMALE CELLS. 261

inner narrower portion with a diameter of five to five
and a half millimetres, which is too small for a female,
but just large enough fora male. This arrangzement
placed the Osmias in a difficulty. They could not
follow their natural instinct and construct at the end
of the tube cells large enough for females.

What happened? Some of the Osmias shut off the
narrow ends, and used only the outer wider portion.
Others, reluctant, as it were, to throw away a chance,
built also in the narrow part of the tube, and under
these circumstances, contrary to the otherwise invari-
able rule, the inner and first constructed cells contained
males.

M. Fabre concludes then, and it seems to me has
given very strong reasons for thinking so, that these
privileged insects not only know the sex of the insect
which will emerge from the egg they are about to lay,
but that at their own will they can actually control it!
Certainly a most curious and interesting result !

He concludes his charming work as follows :—* Mes
chérs insectes, dont |’étude m’a soutenu et continue a
me soutenir au milieu de mes plus rudes épreuves, il
faut ici, pour aujourd’hui, se dire adieu. Autour de
moi les rangs s‘eclaircissent et les longs espoirs ont fui.
Pourrai-je encore parler de vous ?” and every lover of
nature will, I am sure, echo the wish.

CHAPTER XIII.

ON THE SUPPOSED SENSE OF DIRECTION.

ONE of the most interesting questions connected with
the instincts and powers of animals has reference to the
manner in which they find their way back, after having
been carried to a distance from, home. This has by
some been attribited to the possession of a special
“sense of direction.”

Mr. Darwin suggested that it would be interesting
to try the effect of putting animals “in a circular box
with an axle, which could be made to revolve very
rapidly, first in one direction and then in another, so
as to destroy for a time all sense of direction in the
insects. I have sometimes,” he said, “imagined that
animals may feel in which direction they were at the
first start carried.” In fact, in parts of France it is
considered that if a cat is carried from one house to
another in a bag, and the bag is whirled round and
round, the cat loses her direction and cannot return to
her old home.

On this subject M. Fabre has made some interesting
and amusing experiments. He took ten bees belonging
to the genus Chalicodoma, marked them on the back
with a spot of white, and put them in a bag. He
then carried them half a kilometre in one direction,
stopping at a point where an old cross stands by the

EXPERIMENTS WITH BEES. 263

wayside, and whirled the bag rapidly round his head.
While he was doing so a good woman came by, who
was not a little surprised to find the professor stand-
ing in front of the old cross, solemnly whirling a bag
round his head, and, M. Fabre fears, strongly suspected
him of some satanic practice. However this may be,
M. Fabre, having sufficiently whirled his bees, started off
back in the opposite direction, and carried his prisoners
to a distance from their home of three kilometres.
Here he again whirled them round, and then let them
go one by one. They made one or two turns round
him, and then flew off in the direction of home. In the
meanwhile his daughter Antonia was on the watch.
The first bee did the mile and three-quarters in a
quarter of an hour. Some hours after two more re-
turned; the other seven did not reappear.

The next day he repeated this experiment with ten
other bees. ‘The first returned in five minutes, and two
more in about an hour. In this case, again, seven out
of ten failed to find their way home.

In another experiment he took forty-nine bees.
When let out, a few started wrong, but he says that
“lorsque la rapidité du vol me laisse reconnaitre la
direction suivie;” the great. majority flew homewards.
The first arrived in fifteen minutes. In an hour and
a half eleven had returned, in five hours six more,
making seventeen out of forty-nine. Again he experi-
mented with twenty, of which seven found their way
home. In the next experiment he took the bees rather
further—to a distance of about two anda quarter miles.
In an hour and a half two had returned, in three hours
and a half seven more ; total, nine out of forty. Lastly,
he took thirty bees: fifteen marked rose he took by

*

2.64 WHIRLING BEES.

a roundabout route of over five miles; the other fifteen
marked blue he sent straight to the rendezvous, about
one and a half miles from home. All the thirty were
let out at noon; by five in the evening seven “rose”
bees and six “blue” bees had returned, so that the
long détour had made no appreciable difference.
These experiments seem to M. Fabre conclusive. “La
démonstration,” he says, “est suffisante. Ni les mouve-
ments encheyvétrés d’une rotation comme je l’ai décrite; ni
Vobstacle de collines a franchir et de bois 4 traverser; ni
les embichesd’une voie qui s avance, rétrograde et revient
par un ample circuit, ne peuvent troubler les Chali-
codomes dépaysés et les empécher de revenir. au nid.” *

I am not ashamed to confess that, charmed by M.
Fabre’s enthusiasm, dazzled by his eloquence and
ingenuity, I was at first disposed to adopt this view.
Calmer consideration, however, led me to doubt, and
though M. Fabre’s observations are most ingenious, —
and are very amusingly described, they do not carry
conviction to my mind. There are two points specially
to be considered—

1. The direction taken by the bees when released.

2. The success of the bees in making good their
~ return home.

As regards the first point, it will be observed that the
successful bees were in the following proportion, viz. :—

3 out of 10

ey eee |

cy Some Seay

y kee

9 fied

7 iat eas

Or altogether 47 ,, 144

* J. H. Fabre, “ Nouveaux Souvenirs Entomologiques.”

BEHAVIOUR OF BEES IF TAKEN FROM HOME. 265

This is not a very large proportion. Out of the
whole number no less than ninety-seven appear to
have lost their way. May not the forty-seven have
found theirs by sight or by accident? Instinct, how-
ever inferior to reason, has the advantage of being
generally unerring. When two out of three bees went
wrong, we may, I think, safely dismiss the idea of
instinct. Moreover, the distance from home was only
one and a half to two miles. Now, bees certainly
know the country for some distance round their home ;
how far they generally forage I believe we have no
certain information, but 1t seems not unreasonable to
suppose that if they once came within a mile of their
nest they would find themselves within ken of some
familiar landmark. Now, if we suppose that 150 bees
are let out two miles from home, and that they flew
away at random, distributing themselves equally in all
directions, a little consideration will show that some
twenty-five of them would find themselves within a mile
of home, and consequently would know where they were.
I have never myself experimented with Chalicodomas,
but I have observed that if a hive bee is taken to a
distance, she behaves as a pigeon does under similar
circumstances ; that is to say, she flies round and round,
eradually rising higher and higher and enlarging her
circle, until I suppose her strength fails or she comes
within sight of some known object. Again, if the bees
had returned by a sense of direction, they would have
been back in a few minutes. To fly one and a half or
two miles would not take five minutes. One bee out of
the 147 did it in that time; but the others took one,
two, three, or even five hours. Surely, then, it is
reasonable to suppose that these lost some time before

266 MODE OF FINDING THEIR WAY.

they came in sight of any object known to them. The
second result of M. Fabre’s observations is not open to
these remarks. He observes that the great majority
of his Chalicodomas at once took the direction home.
He confesses, however, in the sentence I have already
quoted, that it is not always easy to follow bees with
the eye. Admitting the fact, however, it seems to me
far from impossible that the bees knew where they
were ; and, at any rate, this does not seem so improbable
that we should be driven to admit the existence of a
new sense, which we ought only to assume as a last
resource.

Moreover, M. Fabre himself says, “ Lorsque la rapidité
du vol me laisse reconnaitre la direction suivie,” which
seems to imply a doubt. Indeed, some years previously
he had made a similar experiment with the same
species, but taking them direct to a point rather over
two miles (four kilometres) from the nest, and not
whirling them round his head. I looked back, there,
fore, to his previous work to see how these behaved,
and I found that he says—

“ Aussit6t libres, les Chalicodomes Faden comme
effarés, qui dans une direction, qui dans la direction
tout opposée. Autant que le permet leur vol fougueux,
je crois néanmoins reconnaitre un prompt retour des
abeilles lancées a l’opposé de leur demeure, et Ja majorité
me semble se diriger du cété de Vhorizon ot se trouve
le nid. Je laisse ce point avec des doutes, que rendent
inévitables des insectes perdus de vue a une vingtaine
de métres de-distance.”

In this case, then, some went in one direction, some
in another. It certainly would be remarkable if bees
which were taken direct missed their way, while those

EXPERIMENTS WITH ANTS. 267

which were whirled round and round went straight
home.

Moreover, it appears that after all, as a matter of fact,
they did not fly straight home. Ifthey had done so they
would have been back in three or four minutes, whereas
they took far longer. Even then, if they started in the
right direction, it is clear that they did not adhere
to it. J have myself tried experiments of the same
kind with hive bees and ants. For instance, I put
down some honey on a piece of glass close to a nest
of Lasius mger, and when the ants were feeding I
placed it quietly on the middle of a board one foot
square, and eighteen inches from the nest. I did
this with thirteen ants, and marked the points at
which they left the board. Five of them did so on
the half of the board nearest the nest, and eight on
that turned away from it. I then timed three of
them. ‘They all found the nest eventually, but it took
them ten, twelve, and twenty minutes respectively.
Again, I took forty ants which were feeding on some
honey, and put them down on a gravel-path about fifty
yards from the nest, and in the middie of a square
eighteen inches in diameter, which I marked out on
the path by straws.

I prepared a corresponding square on paper, and,
having indicated by the arrow the direction of the nest,
{ marked down the spot where each ant passed the
boundary. ‘They crossed it in all directions; and
dividing the square into two halves, one towards the
nest and one away from it, the number in each were
almost exactly the same.

_ After leaving the square, they wandered about with
every appearance of having lost themselves, and crossed

268 MR. ROMANES’ EXPERIMENTS.

the boundary backwards and forwards in all directions,
T'wo of them, however, we watched for an hour -each.
They meandered about, and at the end of the time
one was about two feet from where she started, but
scarcely any nearer home; the other about six feet
away, and nearly as much further from home. I then
took them up and replaced them near the nest, which
they at once joyfully entered.

I mentioned some of the foregoing facts in a paper
which I read at the meeting of the British Association
at Aberdeen, and they have since been confirmed by
Mr. Romanes.* |

“In connection,” he says, “ with Sir John Lubbock’s
paper at the British Association, in which this subject
is treated, it is perhaps worth while to describe some
experiments which I made last year. The question to
be answered is whether bees find their way home
merely by their knowledge of landmarks, or by means
of some mysterious faculty usually termed a sense of
direction. ‘The ordinary impression appears to have
been that they do so in virtue of some such sense, and
are therefore independent of any special knowledge of
the district in which they may be suddenly liberated ;
and, as Sir John Lubbock observes, this impression was
corroborated by the experiments of M. Fabre. The
conclusions drawn from these experiments, however,
appeared to me, as they appeared to Sir John, un-
warranted by the facts; and therefore, like him, I re-
peated them with certain variations. In the result I
satisfied myself that the bees depend entirely upon their
special knowledge of district or landmarks, and it is
because my experiments thus fully corroborate those

* Nature, October 29, 1886.

/

MR. ROMANES’ EXPERIMENTS. 269

which were made by Sir John that it now occurs to me
to publish them.

“The house where I conducted the observations is
situated several hundred yards from the coast, with
flower-gardens on each side, and lawns between the
house and the sea. Therefore bees starting from the
house would find their honey on either side of it, while
the lawns in front would be rarely or never visited—
being themselves barren of honey, and leading only to
the sea. Such being the geographical conditions, I
placed a hive of bees in one of the front rooms on the
- basement of the house. When the bees became
thoroughly well acquainted with their new quarters by
_ flying in and out of the open window for a fortnight, I
began the experiments. ‘The modus operandi consisted
in closing the window after dark when all the bees were
in their hive, and also slipping a glass shutter in front
of the hive door, so that all the bees were doubly im-
prisoned. Next morning I slightly raised the glass
shutter, thus enabling any desired number of bees to
escape. When the desired number had escaped, the
glass shutter was again closed, and all the liberated
bees were caught as they buzzed about the inside of the
shut window. ‘These bees were then counted into a box,
the window of the room opened, and a card well smeared
over with birdlime placed upon the threshold of the
beehive, or just in front of the closed glass shutter,
The object of all these arrangements was to obviate the
necessity of marking the bees, and so to enable me not
merely to experiment with ease upon any number of
individuals that I might desire, but also to feel confident
that no one individual could return to the hive un-
noticed. For whenever a bee returned it was certain

270 MR. ROMANES’ EXPERIMENTS.

to become entangled in the bird-lime, and whenever I
found a bee so entangled, I was certain that it was one
which I had taken from the hive, as there were no other |
hives in the neighbourhood.

“Such being the method, I began by taking a score ot
bees in the box out to sea, where there could be no Jand-
marks to guide the insects home. Had any of these
insects returned, I should next have taken another score
out to sea (after an interval of several days, so as to be
sure that the first lot had become permanently lost),
and then, before liberating them, have rotated the box
in a sling for a considerable time, in order to see whether
this would have confused their sense of direction. But,
as none of the bees returned after the first experiment,
it was clearly needless to proceed to the second. Ac-
cordingly, I liberated the next lot of bees on the sea-
shore, and, as none of these returned, I liberated another
lot on the lawn between the shore and the house. I
was somewhat surprised to find that neither did any of
these return, although the distance from the lawn to
the hive was not above two hundred yards. Lastly, I
liberated bees in different parts of the flower-garden,
. and these I always found stuck upon the bird-lime
within a few minutes of their liberation. Indeed, they
often arrived before I had had time to run from the
place where I had liberated them to the hive. Now,
as the garden was a large one, many of these bees had >
to fly a greater distance, in order to reach the hive,
than was the case with their lost sisters upon the lawn,
and therefore I could have no doubt that their uniform
success in finding their way home so immediately was
due to their special knowledge of the flower-garden,
and not to any general sense of direction. |

—

NO EVIDENCE OF SEPARATE SENSE OF DIRECTION. 271

“I may add that, while in Germany a few weeks ago,
I tried on several species of ant the same experiments
as Sir John Lubbock describes in his paper as having
been tried by him upon English species, and here also I
obtained identical results; in all cases the ants were
hopelessly lost if liberated more than a moderate dis-
tance from their nest.

M. Romanes’ experiments, therefore, as he himself
says, entirely confirm the opinion I have ventured to
express—that there is no sufficient evidence among
insects of anything which can justly be called a “ sense
of direction.”

CHAPTER XIV.

ON THE INTELLIGENCE OF THE DOG.

CONSIDERING the long ages during which man and
the other animals have shared this beautiful world,
it is surely remarkable how little we know about them.
We have recently had various interesting works on
the intelligence and senses of animals, and yet I think
the principal impression which they leave on the mind
is that we know very little indeed on the subject.

THE Doa.

As to the intelligence of the dog, a great many
people, indeed, seem to me to entertain two entirely
opposite and contradictory opinivns. I often hear it
said that the dog, for instance, is very wise and clever.
But when I ask whether a dog can realize that two and
two make four, which is a very simple arithmetical
calculation, I generally find much doubt expressed.

That the dog is a loyal, true, and affectionate friend
must be gratefully admitted, but when we come to con-
sider the psychical nature of the animal, the limits of our
knowledge are almost immediately reached. I have else-
where suggested that this arises in great measure from
the fact that hitherto we have tried to teach animals,
rather than to learn from them—to convey our ideas to

EDUCATION OF THE DEAF AND DUMB. 273

them, rather than to devise any language or code of
signals by means of which they might communicate
theirs to us. The former may be more important
from a utilitarian point of view, though even this is
questionable, but psychologically it is far less interest-
ing. Under these circumstances, it occurred to me
whether some such system as that followed with deaf
mutes, and especially by Dr. Howe with Laura Bridg-
man, might not prove very instructive if adapted to the
ease of dogs.

A very interesting account of Laura Bridgman has
been published by Wright, compiled almost entirely from
reports of the Perkins Institution, and the Massachusetts
Asylum for the Blind, in which Dr. Howe, the director
of the establishment, details the history of Laura Bridg-
man, who was deaf, dumb, and blind, almost without the
power of smell and taste, but who, nearly alone among
those thus grievously afflicted, possessed an average, if
not more than an average, amount of intelligence,
although, until brought under Dr. Howe’s skilful treat-
ment and care, her physical defects excluded her from
all social intercourse.

Laura Bridgman was born of intelligent and respect-
able parents, in Hanover, New Hampshire, U.S., in
December, 1829. She is said to have been a sprightly,
pretty infant, but subject to fits, and altogether very
fragile. At two years old she was fairly forward, had
mastered the difference between A and B, and, indeed,
is said to have displayed a. considerable degree of
intelligence. She then became suddenly ill, and had
to be kept in a darkened room for five months. When
she recovered she was blind, deaf, and had nearly lost
the power both of smell and taste.

274 LAURA BRIDGMAN.

“What a situation was hers! The darkness and
silence of the tomb were around her; no mother’s smile
gladdened her heart, or ‘called forth an answering
smile;’ no father’s voice taught her to imitate his
sounds. ‘I’o her, brothers and sisters were but forms
of matter, which resisted her touch, but which differed
not from the furniture of the house, save in warmth
and in the power of locomotion, and in these ——
not even from the dog or cat.”

Her mind, ae was unaffected, and the sense
of touch remained. “As soon as she was able to walk,
Laura began to explore the room, and then the house;
she became familiar with the form, density, weight,
and heat of every article she could lay her hands on.

“She followed her mother, felt her hands and arms,
as she was occupied about the house, and her disposi-
tion to imitate led her to repeat everything herself.
She even learnt to sew a little, and to knit. Her
affections, too, began to expand, and seemed to be
lavished upon the members of her family with peculiar
force.

“The means of communication with her, however,
were very limited. She could only be told to go to
a place by being pushed, or to come to one by a sign
of drawing her. Patting her gently on the head
- signified approbation ; on the back, the contrary.”

The power of communication was thus most limited,
and her character began to suffer, when fortunately Dr.
Howe heard of her, and in October, 1837, received her
into the institution. |

“Fora while she was much bewildered, till she became
acquainted with her new locality, and somewhat familiar
with the inmates; the attempt was made to give her

LAURA BRIDGMAN. 215

knowledge of arbitrary signs, by which she could
interchange thoughts with others.

“The first experiments were made by taking the
articles in common use, such as knives, forks, spoons,
keys, etc., and pasting upon them labels, with their
names embossed in raised letters. These she felt
carefully, and soon, of course, distinguished that the
crooked lines s-p-o-o-n differed as much from the
crooked lines k-e-y, as the spoon differed from the key
in form. Then small detached labels with the same
words printed upon them were put into her hands;
she soon observed that they were the same as those
pasted upon the articles. She showed her perception
of this similarity by laying the label k-e-y upon the
key, and the label s-p-o-o-n upon the spoon.

“ Hitherto, the process had been mechanical, and the
success about as great as that of teaching a very know-
ing dog a variety of tricks.

“The poor child sat in mute amazement, and patiently
imitated everything her teacher did. But now her
intellect began to work, the truth flashed upon her, and
she perceived that there was a way by which she could
herself make a sign of anything that was in her own
mind, and show it to another mind. At once her
countenance lighted up with a human expression. It
was no longer as a mere instinctive animal; it was an
immortal spirit, eagerly seizing upon a new link of
union with other spirits. I could almost fix upon the
moment when this truth dawned upon her mind, and
spread its beams upon her countenance; I saw that the
ereat obstacle was overcome, and that henceforth
nothing but patient and persevering, but plain and
straightforward, efforts were necessary.

276 APPLICATION OF THE METHOD FOLLOWED

“The result, thus far, is quickly related and easily
conceived; but not so was the process, for many weeks
of apparently unprofitable labour were spent before it
was effected. |

“The next step was to procure a set of metal types,
with the different letters of the alphabet cast separately
on their ends; also a board, in which were square holes,
into which she could set the types, so that the letters
could alone be felt above the surface.

“Thus, on any article being handed to her, as a pencil
or watch, she would select the component letters and
arrange them on the board, and read them with apparent
pleasure, assuring her teacher that she understood by
taking all the letters of the word and putting them to
her ear, or on the pencil.”

It is unnecessary, from my present point of view, to
carry the narrative further, interesting as it is. I will
only observe that even in the case of Laura Bridgman
the process was one of much difficulty and requiring
great patience. For a long while it was found im-
possible to make her realize the use of adjectives; she
could not “understand any general expression of
quality.” Again, we are told that “Some idea of the
difficulty of teaching her common expressions may be
derived from the fact that a lesson of two hours upon
the words ‘right’ and ‘left’ was deemed very profitable
if she had in that time really mastered the idea.”

Now, it seemed to me that the ingenious method
devised by Dr. Howe, and so successfully carried
out in the case of Laura Bridgman, might be adapted
to the case of dogs, and I have tried this in a small
way with a black poodle named Van.

WITH THE DEAF AND DUMB TO ANIMALS. 277

VAN AND HIS CARDS.

I took two pieces of cardboard about ten inches by
three, and on one of them printed in large letters the

word
FOOD

leaving the other blank. I then placed the two
cards over two saucers, and in the one under the
“food” card put a little bread and milk, which
Van, after having his attention called to the card,
was allowed to eat. ‘This was repeated over and over
again till he had had enough. In about ten days he
began to distinguish between the two cards. I then
put them on the floor and made him bring them to
me, which he did readily enough. When he brought
the plain card I simply threw it back, while when he
brought the “food” card I gave him a piece of bread,
and in about a month he had pretty well learned to
realize the difference. I then had some other cards
printed with the words “ out,” “tea,” “bone,” “ water,”
and a certain number also with words to which
I did not intend him to attach any significance, such
as “nought,” “plain,’ “ball,” etc. Van soon learned
that bringing a card was a request, and soon learned
to distinguish between the plain and printed cards;
it took him longer to realize the difference between
words, but he gradually got to recognize several, such
as “food,” “ out,” “* bone,’ “tea,” ete. If he was asked
whetber he would like to go out for a walk, he would
joyfully fish up the “out” card, choosing it from
several others, and bring it to me, or run with it in
evident triumph to the door.

278 MY DOG VAN.

T need hardly say that the cards were not always put
in the same places. They were varied quite indiscrimi-
nately and in a great variety of positions. Nor could
the dog recognize them by scent. ‘They were all alike,
and all continually handled by us. Still, I did not trust
to that alone, but had a number printed for each word.
When, for instance, he brought a card with “food” on
it, we did not put down the same identical card, but
another bedring the same word; when he had brought
that, a third, then a fourth, and so on. For a single
meal, therefore, eighteen or twenty cards would he-
used, so that he evidently is not guided by scent. No
one who has seen him look down a row of cards and
pick up the one he wanted could, I think, doubt that
in bringing a card he felt that be is making a
request, and that he could not only distinguish one
card from another but also associate the word and
object. |

I used to leave a card marked “ water” in my dress-
ing-room, the door of which we used to pass in going
to or from my sitting-room. Van was my constant
companion, and passed the do:r when I was at home
several times in the day. Generally he tovk no heed
of the card. Hundreds, or I may say thousands, of
times he passed it unnoticed. Sometimes, however, he
would run in, pick it up, and bring it to me, when of
course I gave him some water, and on such occasions I
invariably found that he wanted to drink.

I might also mention, in corroboration, that one
morning he seemed unwell. A friend, being at break-
fast with us, was anxious to see him bring his cards, and
I therefore pressed him to do so. To my surprise he
brought three dummy cards successively, one marked

COMMUNICATION BY MEANS OF CARDS, 279

“ham,” one “bag,” and one “brush.” TI sgaid re-
proachfully, “Oh, Van! bring “food,” or “tea;” on
which he looked at me, went very slowly, and brought
the “tea” card. But when I put some tea down as
usual, he would not touch it. Generally he greatly
enjoyed acup of tea, and, indeed, this was the only
time I ever knew him refuse it.

A definite numerical statement always seems to me
clearer and more satisfactory than a mere general
assertion. I will, therefore, give the actual particulars
of certain days. ‘Twelve cards were put on the floor,
one marked “food” and one “tea.” The others had more
or less similar words. I may again add that every time
a card was brought, another similarly marked was put
in its place. Van was not pressed to bring cards, but
simply left to do as he pleased.

1 Van brought “food” 4 times. “Tea” 2 times,

2 ” ” 6 9

3 $9 39 8 ry) ry) ae

4 Pa 39 é 99 39 3 ry)

5 ” 9 6 ” 9 eee

6 ” ” 6 le * Nought” onee.

7 39 9 ists, » 4 9

8 ” 99 ae 29 3 29

9 ” 3? 4 Ey) ” 2 5
10 7 ” 10 9 99 - ? * Door” once.
11 99 ” 10 ” oy) 3 29
12 3 9 ae 99 355

80 31

Thus out of 113 times he brought food 80 times, tea
31 times, and the other 10 cards only twice. Moreover,
the last time he was wrong he brought a card—namely,
“door ’”—in which three letters out of four were the

same as in “ food.”
14

280 ATTEMPTS TO CONVEY IDEAS.

This is, of course, only a beginning, but it is, I
venture to think, suggestive, and might be carried
further, though the limited wants and aspirations of
the animal constitute a great difficulty. My wife has
a beautiful and charming collie, Patience, to whom we
are much attached. This dog was often in the room
when Van brought the “food” card and was rewarded
with a piece of bread. She must have seen this thou-
sands of times, and she begged in the usual manner,
but never once did it occur to her to bring a card.
She did not touch, or, indeed, even take the slightest
notice of them. 7 +

I then tried the following experiment :—I prepared
six cards about ten inches by three, and coloured in
pairs—two yellow, two blue, and two orange. I put one
card of each colour on the floor, and then, holding up one
of the others, endeavoured to teach Van to brmg me
the duplicate. That is to say, that if the blue was
held up, he should fetch the corresponding colour from
the floor ; if yellow, he should fetch the yellow, and
soon. When he brought the wrong card he was made
to drop it and return for another, until he brought the
right one, when he was rewarded with a little food.

We continued the lessons for nearly three months,
but asa few days were missed, we may say for ten
weeks, and yet at the end of the time I cannot say that
Van appeared to have the least idea what was expected
of him. It seemed a matter of pure accident which
card he brought. There is, I believe, no reason to
doubt that dogs can distinguish colours; but as it was
just possible that Van might be colour-blind, we then
repeated the same experiment, only substituting for the
coloured cards others marked respectively with one,

ARITHMETICAL POWERS OF ANIMALS. 281

two, and three dark bands. This we continued for
another three months, or, say, allowing for intermissions,
ten weeks ; but, to my surprise, entirely without success,
for we altogether failed to make Van understand what
we wanted. I was rather disappointed at this, as, if
it had succeeded, the plan would have opened out many
interesting lines of inquiry. Still, in such a case one
ought not to wish for one result more than another
as, of course, the object of all such experiments is
merely to elicit the truth, and our result in the present
case, though negative, is very interesting. I do not,
however, regard it as by any means conclusive, and
should be glad to see it repeated. If the result proved
to be the same, it would certainly imply very little
power of combining even extremely simple ideas.

Can ANIMALS COUNT ?

I then endeavoured to get some insight into the
arithmetical condition of the dog’s mind. On this
subject I have been able to find but little in any of
the standard works on the intelligence of animals.
Considering, however, the very lmited powers of
savage men in this respect—that no Australian
language, for instance, contains numerals even up to
four, no Australian being able to count his own fingers
even on one hand—we cannot be surprised if other
animals have made but little progress. Still, it is
curious that so little attention should have been
directed. to this subject. Leroy, who, though he ex-
presses the opinion that “the nature of the soul of
animals is unimportant,’ was an excellent observer,
mentions a case in which a man was anxious to shoot

282 PREVIOUS OBSERVATIONS.

acrow. “To deceive this suspicious bird, the plan was
hit upon of sending two men to the watch-house, one
of whom passed on, while the other remained; but the
crow counted, and kept her distance. The next day
three went, and again she perceived that only two
retired. In fine, it was found necessary to send five or
six men to the watch-house to put her out in her
calculation. The crow, thinking that this number of
men had passed by, lost no time in returning.” From
this he inferred that crows could count up to four.
Lichtenberg mentions a nightingale which was said to
count up to three. Hvery day he gave it three meal-
worms, one at a time; when it had finished one it
returned for another, but after the third it knew that
the feast was over. I do not find that any of the recent
works on the intelligence of animals, either Buchner,
or Peitz, or Romanes in either of his books, give any
additional evidence on this part of the subject. ‘There
are, however, various scattered notices.

According to my bird-nesting recollections, which I
have refreshed by more recent experience, if a nest
contains four eggs, one may safely be taken; but if
two are removed, the bird generally deserts. Here, then,
it would seem as if we had some reason for supposing
that there is sufficient intelligence to distinguish three
from four.

An interesting consideration rises also with refer-
ence to the number of the victims allotted to each
cell by the solitary wasps. Ammophila considers one
large caterpillar of Noctua segetwm enough; one species
of Eumenes supplies its young with five victims;
one ten, another fifteen, and one even as many as
twenty-four. The number is said to be constant in

SUPPOSED POWERS OF COUNTING. 283

each species. How, then, does the insect know when her
task is fulfilled? Not by the cell being filled, for if
some be removed she does not replace them. When
she has brought her complement she considers her task
accomplished, whether the victims are still there or
‘not. How, then, does she know when she has made
up the number twenty-four? Perhaps it will be said
that each species feels some mysterious and innate
tendency to provide a certain number of victims.
This would not under any circumstances be an ex-
planation, nor is it in accordance with the facts. In
the genus Eumenes the males are much smaller
than the females. Now, in the hive bees, humble
bees, wasps, and other insects where such a differ-
ence occurs, but where the young are directly fed, it
is, of course, obvious that the quantity can be pro-
portioned to the appetite of the grub. But in insects
with the habits of Humenes and Ammophila the case is
different, because the food is stored up once for all.
Now, it is evident that if a female grub was supplied
with only food enough for a male, she would starve to
death ; while if a male grub were given enough fora
female it would have too much. No such waste, how-
ever, occurs. In some mysterious manner the mother
knows whether the egg will produce a male or female
erub, and apportions the quantity of food accordingly.
She does not change the species or size of her prey;
but if the ege is male she supplies five, if female ten,
victims. Does she count? Certainly this seems very
like acommencement of arithmetic. At the same time,
it would be very desirable to have additional evidence
before we can arrive at any certain conclusion.
Considering how much has been written on instinct,

284 MR. HUGGINS’S EXPERIMENT.

it seems surprising that so little attention has been
directed to this part of the subject. One would fancy
that there ought to be no great difficulty in determining
how far an animal can count; and whether, for in-
stance, it could realize some very simple sum, such as
that two and two make four. But when we come to
consider how this is to be done, the problem ceases to
appear so simple. We tried our dogs by putting a
piece of bread before them, and preventing them from
touching it until we had counted seven. To prevent
ourselves from unintentionally giving any indication,
we used a metronome (the instrument used for marking
time when practising the pianoforte), and to make the
beats more evident we attached a slender rod to the
pendulum. It certainly seemed as if our dogs knew
when the moment of permission had arrived ; but their
movement of taking the bread was scarcely so definite
as to place the matter beyond a doubt. Moreover,
dogs are so very quick in seizing any indication given
them, even unintentionally, that, on the whole, the
attempt was not satisfactory to my mind. I was the
more discouraged from continuing the experiment in
this manner by an account Mr. Huggins gave me ofa
very intelligent dog belonging to him. A number of
cards were placed on the ground, numbered respectively
1, 2,3, and soonup to10. A question was then asked :
the square root of 9 or 16, or such a sum as 6495 —3.
Mr. Huggins pointed consecutively to the cards, and
the dog always barked when he came to the right one.
Now, Mr. Huggins did not consciously give the dog any
sion, yet so quick was the dog in seizing the slightest
indication, that he was able to give the correct answer.

“The mode of procedure is this, His master tells

CONCLUSION. 285

him to sit down, and shows him a piece of cake. He is
then questioned, and barks his answers. Say he is
asked what is the square root of 16, or of 9; he will
bark four or three times, as the case may be. Or
such a sum as ***+7-5 he will always answer correctly.
The piece of cake is, of course, the meed of such
cleverness. It must not be supposed that in these
performances any sign is consciously made by his
questioner. None whatever. We explain the per-
formance by supposing that he reads in his master’s
expression when he has barked rightly; certainly he
never takes his eyes from his master’s face.” *

This observation seems to me of great interest in
connection with the so-called “thought-reading.” No
one, I suppose, will imagine that there was in this
case any “thought-reading” in the sense in which
this word is generally used. Evidently “Kepler”
seized upon some slight indication unintentionally
given by Mr. Huggins. The observation, however,
shows the great difficulty of the subject.

The experiments I have made are, I feel, very
incomplete, but I have ventured to place them on
record, partly in hope of receiving some suggestions,
and partly in hope of inducing others with more
leisure and opportunity to carry on similar observa-
tions, which I cannot but think must lead to interesting
results.

* M. L. Huggins, “ Kepler: a Biography.”

INDEX.

A

Acalles, 66

Acanthopleura, 15, 145

Acheta, 61, 63, 97, 117

Acridiide, 100, 106

Actinia, 13

Ageronia, 73

Aglaura, 188

Alciopide, 14, 22, 137

Ammophila, 243, 282

Amphibia, 32, 129

Amphicora, 87

Amphioxus, 129

Angler, 186

Anguis, 126

Annelides, touch, 13; taste, 22;
smell, 34; hearing, 87; sight, 134;
problematical organs, 189

Anobium, 67

Anoxia, 251

Anthidium, 71

Anthrax, 251

Ants, 24, 31, 43, 56, 69, 107, 115,
178, 202

Apion, 94

Apis, 26, 29, 58, 69, 70, 115, 150,
172, 194, 258, 283

Arca, 141

Arenicola, 87

Arithmetic of animals, 281

Arthropods, touch, 16; taste, 23;
smell, 35; hearing, 88; sight, 146;
problematical organs, 188

Articulata. See Annelides, Insects

Ascidians, 129

Asellus, 48

Astacus, 23, 51, 88
Asteracanthion, 133

Asterope, 22

Astropecten, 132

Ateuches, 66

Auditory hairs, 16, 79, 85, 88, 118
organs, 77

rods, 18, 104, 111

EB

Balanus, 220

Bee, hive. See Apis

Bee, solitary, 242

Beetles. See Coleopter
Bembex, 242, 246

Birds, 129, 282

Blatta, 46, 152

Blethisa, 68

Blind spot in eye, 125
Bohemilla, 13, 134
Bombardier beetle, 65
Bombus, 28, 70, 73, 178, 283
Bostrychida, 67

Brachinus, 64, 68
Brachyura, 90

Butterfly. See Lepidoptera

f
id

Calanella, 159
Calotis, 127
Callianassa, 59

288

Camponotus, 208

Capitellide, 34

Capricorn beetle, 96

Carcinus, 92

Cards, Van and his, 277

Carinaria, 87

Caterpillars, 23, 243, 259

Cats, 262

Centipedes, 49, 74

Cephalopoda, 34, 141

Cerambyx, 67, 95, 96

Ceratius, 186

Ceratophyus, 68

Chalcidide, 27

Chalicodoma, 251, 262

Chiasognathus, 68

Chitons, 15, 144

Cicadas, 61, 64, 151

Cicadida, 151

Clepsine, 134

Cockchafer. See Melolontha

Cockroach, 46, 152

Celenterata, touch, 11; taste, 22;
smell, 33; hearing, 82; sight, 131

Coleoptera, 58, 67, 111, 151

Collie, 280

Color of deep-sea fish, 185

of flowers, 199

, sense of, 190, 194, 202, 280

Componotus, 239

Compound eyes, 163

Copepoda, 48

Copilia, 158

Copris, 68, 95

Corephium, 145

Corethra, 18, 113, 117, 151

Corixa, 75

Corti, the organ of, 80, 108

Coryceus, 157

Cossus, 148

Count ? can animals, 281

Crabs, 90, 92

Crayfish. See Astacus

Cricket. See Acheta

Crioceris, 68

Crow, 282

Crustacea, touch, 16; taste, 23;
smell, 46; hearing, 88; sight, 156;
sense of color, 211; problematical
organs, 188

Crystalline cone, 166

INDEX

Culex, 68, 115
Curculionide, 68
Cychrus, 68
Cyclostoma, 140
Cymbulia, 88

D

Daphnia, 48, 206, 212
Dead-nettle, 200

Death-watch, 66

Dias, 220

Dinetus, 39

Diptera, 52, 69, 110, 149, 151
Direction, sense of, 262

Dog, intelligence of the, 272
Dragon-fly. See Libellula
Dytiscus, 5, 6, 112, 131, 146, 167

K

See Auditory organs
in tail of Mysis, 92
, structure of the human, 78, 101
Earthworms, 206
Elaphrus, 68
Elaterida, 67
Empusa, 176
Endosmosis, 25
Englena, 130
Epeira, 146
Ephippigera, 103
Epithelial cells, 14, 20
Epithelium, 11, 19
Eristalis, 69, 174, 176
Eucopide, 85
Eucorybar, 74
Eumenes, 245, 282
Euphausia, 161
EKurycopa, 189
Eutima, 83
Evaneade, 27
Eye, compound, 163
of man, 121
——,, pineal, 126
, simple, 170

Ear.

B

Fish, 182
Flowers, 200

INDEX. 289

Fly. See Musca
Forficula, 151, 167
Formica. See Ants

G

Gammarus, 49, 188
Gasteropods, 86

Geotrupes, 68

Geryonia, 86

Glomeris, 50
Glossopharyngeal nerves, 19
Gnat, 68, 115

Gryllotalpa, 102

Gryllus, 63, 98, 106, 108

H

Hairs, auditory, 16, 79, 85, 88, 116

, depressed, 17

——,, flattened, 56

——, glandular, 29

» hollow, 17

in insects, 16

of touch. Sce Tactile

, olfactory, 16, 25

, ordinary surface, 16, 56

——-, plumose natatory, 16, 94

, simple, 18

, solid, 17, 82

, tactile, 16, 18, 28, 29, 56

, taste, 16, 28

Haliotis, 5, 139

Hattaria, 127

Hearing, organs of, in Vertebrata, 77 ;
Celenterata, 82; Mollusca, 86;
Annelida, 87; Arthropods, 88

, sense of, 60, 97

Helix, 14, 139

Hemiptera, 112, 151

Hesione, 135

Humble-bee. See Bombus

Hydaticus, 40

Hydrachna, 28

Hydromeduse, 86

Hydrophilus, 168

Hydrozoa, 13

Hyleus, 58

Hymenoptera, 23, 25, 56, 57, 58, 69,

“70, 96, 151, 181, 250

Hyperia, 171
Hypoderm, 5, 16

i

Ichneumon, 54, 58
Ichthyosaurus, 129
Infusoria, 11
Insects, touch, 16; taste, 233; smell,
35, 52; hearing, 61, 94; sight,
146; problematical organs, 188
Instinct—
Ant, 202, 232, 267
Bee, hive, 194, 253
, solitary, 255, 260, 262
Birds, 282
Bombardier beetle, 64
Change in, 244
Crustacea, 90
Daphnia, 229
Dog, 272
Fish, 186
Fly, 174, 177
Limitation of, 253
Of direction, 262
Onchidium, 144
Paussus, 65
Wasp, solitary, 245, 282
Isopteryx, 109

J
Jelly-fish. See Medusx
Julus, 49

L

Labyrinthodons, 129

Lacerta, 126, 128

Lamellibranchiata, 14, 141

Lamellicornia, 37, 52

Lamium, 200

Lampyris, 167

Lancelet, 129

Lasius. See Ants

Laura Bridgman, 273

Leech, 189

Lema, 68

Lepidoptera, 37, 71, 94, 111, 148,
fol, 168, Wel

Leptodora, 156

290

Leucospis, 251

Libellula, 69, 70, 149, 152, 171
Light-organs, 161, 185

Ligia, 167

Limitation of instinct, 253
Limpet, 4, 138

Limulus, 159

Lithobius, 155

Lizzia, 132

Lobster, 90, 91

Locusts, 62, 99, 106, 111, 149, 176
Longicorn beetles, 66, 95
Lucanus, 43, 52

Lucilia, 177

Lycosa, 179

Lyda, 58

M

Mammals, 129
Maxille, 25
Meconema, 102, 105
Meduse, 6, 22,
117
Meissner’s corpuscles, 7

Melolontha, 52, 58, 67, 68, 148, 152,

168
Mesonotum, 67
Metronome, 284
Miltogramma, 254

Mollusca, 14, 22, 34, 61, 86, 120,

137, 140
Mordella, 148
Mosaic vision, 163
Mosquito. See Culex
Moths. See Lepidoptera
Murex, 139

Musca, 17, 29, 30, 45, 53, 58, 68, 71,
110, 113, 148, 153, 165, 172, 174,

177, 254
Mutilla, 69, 70
Myriapods, 155, 205
Myrmica. See Ants
Mysis, 92, 98, 157, 161

N

Nautilus, 140
Necrophorus, 66, 68
Needle cells, 21
Nematocera, 151

82, 88, 84, 85, 86,

INDEX.

Nematocysts, 12
Nereis, 12, 135
Nesticus, 180
Neuroptera, 111, 151
Newts, 207

Noctua, 73, 243, 282

0

Oceanide, 86
Ocypoda, 61
Odynerus, 247
(Hstrus, 148
Olfactory organs.
smell
Omaloplia, 68
Onchidium, 14, 131, 143
Oniscoide, 170
Ontorchis, 6, 84

See Organs of

| Organs of hearing, 17; 19, 77, 81, 93,

109, 114

af sight, 19, 130, 146

of smell, 17, 88

of taste, 17, 19, 21

—— of temperature, 6, 10

of touch, 11, 14, 17, 19, 131

» problematical, 182

Origin of organs of sense, 3

Orthoptera, 37, 99, 107, 112, 131,
176

Oryctes, 68

Osmia, 251

Otolithes, 52, 82, 84, 85, 89, 90, 91,
92

, possible origin of, 3

E

Pacinian corpuscle, 8
Pagurus, 51
Palemon, 51
Palinurus, 61

Palpi, 30, 37, 38, 39, 41, 73
Paludina, 140
Pamphila, 184
Paniscus, 58

Patella, 138, 140
Paussus, 65

Pectens, 61, 141
Pectunculus, 141

| Pelagia, 86

Pelobius, 68
Periplaneta, 152
Perophthalmus, 144
Pheidole, 108
Phialidium, 85
Photichthys, 185
Pineal eye, 127
Pinnotheres, 51
Piscicola, 134
Platyarthrus, 207
Plesiosaurus, 129
Pleuromona, 189
Podophthalmata, 50, 156
Polydesmus, 189
Polyophthalmus, 33, 98, 134
Pompilus, 58
Ponera, 69

Pontella, 47, 48
Pontinia, 51

Poodle dog, 276
Pressure-point, 10
Prionus, 67
Proctotrupide, 27
Pronotum, 67
Prosobranchiata, 138
Protoplasm, 21
Protozoa, 32, 61
Pteropods, 87
Ptychoptera, 113

EB

Recognition among ants, 234
Reptilia, 127, 130
Respiration in insects, 35
Retina, 123

Rhopalonema, 85

Rods, auditory, 18, 104, 111, 187

, olfactory, 55
» retinal, 124

Ss

Salivary gland, 30
Sarcophaga, 111
Schizochiton, 145
Scolopendra, 155
Scopelus, 186
Scorpions, 179
Sea-anemone, 12, 187

INDEX. 291

Sense-hairs. See Hairs

Sense of direction, 262

Sense-organs, origin of, 3, 86, 111

Senses, unknown, 192

Serolis, 189

Setz. See Hairs

Sex, power of regulating, 262

Sight, organs of, in Vertebrata, 121;
Celenterata, 131; Annelida, 133;
Mollusca, 137; Arthropods, 146

, sense of, 118

——, three possible modes of, 118

Silpha, 38, 41

Sirex, 58

Skin, termination of nerves in, 18

Smell, organs of, in Vertebrata, 32;
Protozoa, 33; Celenterata, 33;
Annelida, 33; Mollusca,34; Arthro-
pods, 35

Smerinthus, 73

Solaster, 133

Sound, organs of, not known in Pro-
tozoa or Celenterata, 61; Mollusca,
61; Crustacea, 61; Insects, 62

Sphex, 245

Sphinx, 73, 148

Spherotherium, 74

Spiders, 74, 146, 155, 170, 178

Spondylis, 67, 141

Squilla, 51

Stag-beetle, 43, 52

Staphylinus, 50

Stenobothrus, 62, 63

Stratiomys, 167

Syrphus, 69, 170

T

Tachytes, 246

Taste, organs of, in Vertebrata, 19;
Annelida, 22; Mollusca, 22; Ar-
thropods, 23

Telephorus, 112

Temperature, organs of, 10

Tenebrionida, 68

Tenthredo, 27, 58

Theridium, 75

Touch, organs of, in Vertebrata, 7 ;
Protozoa, 11; Celenterata, 11;
Meduse, 12; Annelida, 13; Mol-
lusca, 14; Arthropods, 16

vA bela | INDEX.

Touch, sense of, 7 Varanus, 127

Trachee, 29, 30, 101 Vaterian corpuscles, 7
Trachymeduse, 85 Vertebrata, 7, 19, 32, 77
Trachynemade, 157 Vespa, 28, 55, 58, 175, 178, 283
Tritonia, 87

Trochus, 138

Trox, 68 =

Tunicata, 129 Wagner’s corpuscles, 7
Turbellaria, 133 Warmth organs, 6, 10

Wasp. See Vespa

v , solitary, 242, 282
: Weevils, 67, 94
Van, 276 Wolffian glands, 27
Vanessa, 73, 174 Worms. See Annelides

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