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* * * * *
THE
DAWN OF REASON
OR
MENTAL TRAITS IN THE
LOWER ANIMALS
BY
JAMES WEIR, JR., M.D.
New York
THE MACMILLAN COMPANY
LONDON: MACMILLAN & CO., LTD.
1899
_All rights reserved_
* * * * *
COPYRIGHT, 1899,
BY THE MACMILLAN COMPANY.
Norwood Press
J. S. Cushing & Co.--Berwick & Smith
Norwood Mass. U.S.A.
* * * * *
To My Father
WHO, WHILE NOT A SCIENTIST, HAS YET TAKEN
AN INTELLIGENT AND APPRECIATIVE
INTEREST IN MY WORK
THIS BOOK IS RESPECTFULLY DEDICATED
* * * * *
PREFACE
Most works on mind in the lower animals are large and ponderous volumes,
replete with technicalities, and unfit for the general reader; therefore
the author of this book has endeavored to present the evidences of mental
action, in creatures lower than man, in a clear, simple, and brief form.
He has avoided all technicalities, and has used the utmost brevity
consistent with clearness and accuracy. He also believes that metaphysics
has no place in a discussion of psychology, and has carefully refrained
from using this once powerful weapon of psychologists.
Many of the data used by the authors of more pretentious works are
second-hand or hearsay; the author of this treatise, however, has no
confidence in the accuracy of such material, therefore he has not made
use of any such data. His material has been thoroughly sifted, and the
reader may depend upon the absolute truth of the evidence here
presented.
The author does not claim infallibility; some of his conclusions may be
erroneous; he _believes_, however, that future investigation will
prove the verity of every proposition that is advanced in this book. These
propositions have been formulated only after a twenty-years study of
biology in all of its phases.
Some of the data used in this volume have appeared in _Appleton's Popular
Science Monthly_, _Lippincott's Magazine_, _Worthington's Magazine_, _New
York Medical Record_, _Recreation_, _Atlantic Monthly_, _American
Naturalist_, _Scientific American_, _Home Magazine_, _Popular Science
News_, _Denver Medical Times_, and _North American Review_; therefore the
author tenders his thanks to the publishers of these magazines for their
kindness in allowing him to use their property in getting out this work.
"WAVELAND," OWENSBORO, KY.,
January 9, 1899.
* * * * *
CONTENTS
INTRODUCTION
CONSCIOUS AND UNCONSCIOUS MIND
PAGE
Definition of mind--The correlation of physiology, morphology, and
psychology--The presence of nerve-elements in _monera_--Conscious
and unconscious mind--Unconscious ("vegetative") mind in the
jelly-fish--Anatomy, physiology, and psychology of the jelly-fish
--The origin of conscious mind. 1
CHAPTER I
THE SENSES IN THE LOWER ANIMALS
The sense of touch--The senses of taste and smell--Actinophryans having
taste--The sense of sight--Modification of sight organs by surroundings
--Sight in Actinophryans--Blind fish sensitive to light--Blind spiders
--Blind man--Primitive eyes in _Cymothoe_--In the jelly-fish, sea-urchin,
_Alciope_, _Myrianida_--The sight organs of the snail--Power of vision
in the snail--Eyes of crayfish--Compound eyes--Vision in "whirligig
beetle"--In _Periophthalmus_--In _Onchidium_--In _Calotis_--Organs of
audition--In _Lepidoptera_--_Hymenoptera_--_Orthoptera_--_Diptera_
--_Hemiptera_--_Dyticus marginalis_--_Corydalus_--Ears of grasshopper
and cricket--Of the "red-legged locust"--Of flies--Of gnats--Auditory
vesicles of horse-fly--Ears of butterflies--Cerambyx beetle--Long-horned
beetle--_Cicindelidæ_--_Carabidæ_. 7
CHAPTER II
CONSCIOUS DETERMINATION
Definition--How conscious determination is evolved from the senses--The
presence of nerve-tissue in _Stentor polymorphus_--The properties of
nerve-tissue--Romanes' experiment with anemone--Action of stimuli on
nerve-tissue--Reflection--Origin of consciousness--Time element in
consciousness--Conscious determination in _Stentor polymorphus_--In
_Actinophrys_--In _Amoeba_--In _Medusa_--In a water-louse--In a garden
snail--In the angle-worm--In oysters--In a ground wasp. 39
CHAPTER III
MEMORY
Discussed under four heads, viz. _Memory of Locality_ (_Surroundings_),
_Memory of Friends_ (_Kin_), _Memory of Strangers_ (_Other animals not
kin_), and _Memory of Events_ (_Education_, _Happenings_, etc.)--Memory
of locality in _Actinophrys_--In the snail--In the ant--In sand
wasps--In beetles--In reptiles--_Memory of Friends_--In ants
--Experiments with ants, _Lasius flavus_, _Lasius niger_, and
_Myrmica ruginodis_--Memory of kin in wasps and bees--Experiments
--_Memory of Strangers_ (_Animals other than kin_)--Recognition of
enemies--By bumblebees--Memory of individuals not enemies--By the
toad--By the spider--By ants--By snakes--By chameleons--By birds
--By cattle--By dogs--By monkeys--_Memory of Events_ (_Education_, etc.)
--In the wasp--In fleas--In the toad--In other insects. 60
CHAPTER IV
THE EMOTIONS
The higher animals--Laughter--In monkeys--In the dog--In the chimpanzee
--In the orang-utan--Fear, dismay, consternation, grief, fortitude,
joy shown by bees--Affection for the individual evinced by house wren
--Anger, hate, fear, revenge, in the higher animals--Forgiving
disposition in the monkey--Sympathy--In ants--Care of young by ants
--Solicitude of butterflies--Of gadfly--Of the ichneumon fly--Of the
mason wasp--Of the spider--Of the earwig--Anger and hate evinced by
ants, centipedes, tarantulas, weevils. 88
CHAPTER V
ÆSTHETICISM
The love of music--In spiders--In quail--In dogs--Origin of love of
music in the dog--Dog's knowledge of the echo--Love of music in rats
--In mice--Singing mice--Love of music in lizards--In salamanders--In
snakes--In pigeons--In the barnyard cock--In the horse--Amusement and
pastime--In _Actinophrys_--In the snail--In _Diptera_--In ants--In
lady-bugs (_Coccinellæ_)--Æsthetic taste in birds--The snakeskin
bird--Humming-bird--Bower bird--The love of personal cleanliness--In
birds--In insects--In the locust. 107
CHAPTER VI
PARENTAL AFFECTION
Origin of parental feeling--Evidence of this psychical trait in spiders
--In earwigs--In crayfish--In butterflies--In fish--In toads--In
snakes--Instance of pride in parents--In the dog--In the cat--Parental
affection in birds--Animals seeking the assistance of man when their
offspring is in danger--The evolution of parental affection. 134
CHAPTER VII
REASON
Definition of reason--Origin of instincts--Instances of intelligent
ratiocination--In the bee--The wasp--The ant--Mental degeneration in
ants occasioned by the habit of keeping slaves--The honey-making ant
filling an artificial trench--Other evidences of reason in the insect
--_Termes_--Division of labor--The king and queen--Bravery of soldier
ants--Overseer and laborers--Blind impulse and intelligent ideation
--Harvester ants--Their habits and intelligence--Their presence in
Arkansas believed to be unique--Animals able to count--This faculty
present in the mason wasps--Experiments--Certain birds able to count
--Also dogs and mules--Cat recognizing the lapse of time--Monkey's
ability in computing--Huber's experiment with glass slip and bees
--Kirby and Spence's comment--Summary. 147
CHAPTER VIII
AUXILIARY SENSES
The color-changing sense and "homing instinct" so-called--These
faculties not instincts but true senses--The chromatic function
--Tinctumutation--Chromatophores and their function--Various
theories--Experiments of Paul Bert with axolotls--Semper's
contention--The difference between plant coloring and animal
coloring--Effects of light--Experiments with newts--Lister's
observations--Pouchet's experiments--Sympathetic nerves--Author's
experiments with frogs--The sense-centre of tinctumutation--Effects
of atropia--Experiments with fish--With katydid--The "homing instinct"
a true sense--Evidences of the sense in a water-louse--Author's
experiments with snails--Location of sense-centre in snails--Evidences
of the homing sense in the limpet--In beetles--In fleas--In ants--In
snakes--In birds--In fish. 181
CHAPTER IX
LETISIMULATION
Not confined to any family, order, or species of animals--Death-feigning
by rhizopods--By fresh-water annelids--By the larvæ of butterflies and
beetles--By free-swimming rotifers--By snakes--By the itch insect
(_Sarcoptes hominis_)--By many of the _Coleoptera_--The common "tumble
bug" (_Canthon Lævis_) a gifted letisimulant--The double defence of the
pentatomid, "stink-bug"--Reason coming to the aid of instinct--
Death-feigning an instinct--Feigning of death by ants--By a hound--Not
instinctive in the dog and cat--The origin of this instinct--Summary. 202
CONCLUSION
Instinct and reason--Specialized instincts and "intelligent accidents"
--Abstraction in the dog--In the elephant--The kinship of mind in man
and the lower animals shown by the phenomenon of dreaming--By the
effects of drugs--The action of alcohol on rhizopods--On jelly-fish
--On insects--On mammals--Animals aware of the medical qualities of
certain substances--Recognition of property rights--Animals as tool
users--Instinct and reason differentiated--Summary. 215
BIBLIOGRAPHY 225
INDEX 227
* * * * *
DAWN OF REASON
MENTAL TRAITS IN THE LOWER ANIMALS
INTRODUCTION.--CONSCIOUS AND UNCONSCIOUS MIND
Mind is a resultant of nerve, in the beginning of life, neuro-plasmic,
action, through which and by which animal life in all its phases is
consciously and unconsciously, directly and indirectly, maintained,
sustained, governed, and directed.
This definition of mind is widely different from the definition of those
metaphysical scientists who directed psychological investigation and
observation a decade ago. They held that psychology had nothing in
common with physiology and morphology; that _psychos_ stood upon an
independent pedestal, and was not affected by, and did not affect, any
of the phenomena of life.
In these days it is becoming an accepted fact that morphology,
physiology, and psychology are intimately related and connected, and
that a thorough knowledge of the one implies an equally thorough
knowledge of the others.
Morphology and physiology, until a comparatively recent time, led
divergent paths; but, thanks to such men as Haeckel, Romanes, Huxley,
Wolff, and many others, this erroneous method of investigation, to a
great extent, has ceased.
"The two chief divisions of biological research--Morphology and
Physiology--have long travelled apart, taking different paths. This is
perfectly natural, for the aims, as well as the methods, of the two
divisions are different. Morphology, the science of forms, aims at a
scientific understanding of organic structures, of their internal and
external proportions of form. Physiology, the science of functions, on
the other hand, aims at a knowledge of the functions of the organs, or,
in other words, of the manifestations of life."[1]
[1] Haeckel, _Evolution of Man_, Vol. I. p. 20.
Indeed, physiology has so diverged from its sister science, morphology,
that it completely and entirely ignores two of the most important
functions of evolution, heredity and adaptation. This has been clearly
shown by Haeckel, who has done much towards bringing about a change of
opinion in these matters.[2]
[2] _Ibid._, p. 21 _et seq._
Morphology and physiology are interdependent, correlated, and connected
one with the other; and, as I will endeavor to point out as my argument
develops itself, psychology is, likewise, intimately associated with
these two manifestations of life.
It will be noticed that as forms take on more complexity, and as organs
develop new and more complex functions, _psychos_ becomes less simple
in its manifestations, and more complex in its relations to the internal
and external operations of life.
Keeping in view the definition of mind as advanced in the opening
paragraph of this chapter, it at once becomes evident that even the very
lowest forms of life possess mind in some degree. It is true that in the
_monera_, or one-celled organisms, the nerve-cell is not differentiated;
consequently, if I were to be held to a close and strict accountability,
my definition of mind would not embrace these organisms. Yet, some small
latitude must be allowed in all definitions of psychological phenomena,
especially in those phenomena occurring in organisms which typify the
very beginnings of life.
I am confident that, notwithstanding the fact that the nerve-_cell_ is
not differentiated in these primal forms, nerve-elements are,
nevertheless, present in them, and serve to direct and control life.
Mind makes itself evident in two ways--consciously and unconsciously.
The conscious manifestations of mind are volitional, while the
unconscious, "vegetative," reflex operations of mind are wholly
involuntary.
Although the unconscious mind plays fully as prominent a rôle in the
economy of life as does the conscious mind, this treatise will not
discuss the former, except indirectly. Yet, an outline sketch as to what
is meant by the _unconscious_ mind will be necessary, in order that the
reader may more fully comprehend my meaning when discussing _conscious_
mind.
A brief investigation of the anatomy, physiology, and psychology of the
medusa, or jelly-fish, will serve to illustrate the operations of the
unconscious mind as it is to be noticed in its reflex and "vegetative"
phases. The higher and more evolved phases of the unconscious mind will
not be discussed in this work, except incidentally, perhaps, as they may
appear, from time to time, as my propositions are advanced, and the
scheme of mental development is elaborated.
The medusa (the specimen that I take for study is a very common
fresh-water individual) has a well-developed nervous system. Its
transparent, translucent nectocalyx, or swimming-bell, has a central
nervous system which is localized on the margin of the bell, and which
forms the so-called "nerve-ring" of Romanes.[3] This nerve-ring is
separated into an upper and lower nerve-ring by the "veil," an annular
sheet of tissue which forms the floor of the swimming-bell, or
"umbrella," and through a central opening in which the manubrium, or
"handle," of the umbrella passes down and hangs below the margin of the
bell.
[3] Romanes, _Jelly-Fish_, _Star-Fish_, _and Sea-Urchins_, p. 16.
The nerve-ring is well supplied with epithelial and ganglionic
nerve-cells; their function is wholly reflex and involuntary; they
preside over the pulsing or swimming movements of the nectocalyx. This
pulsing is excited by stimulation, and is analogous, so far as movement
is concerned, to the peristaltic action of the intestines. Situated on
the margin of the bell are a number of very minute, round bodies, the
so-called "eyes." These eyes are supplied with nerves, one of whose
functions is volitional, as I will endeavor to show in my chapter on
Conscious Determination.
The manubrium, or handle, is also the centre of a nerve-system. Nerves
proceed from it and are spread out on the inner surface of the bell.
These nerves preside over digestion, and are involuntary. Certain
ganglia in the manubrium appear to preside over volitional effort. I
have never been able, however, to locate their exact position, nor to
determine their precise action. They will be discussed more fully in the
next chapter.
The nervous system of the nectocalyx is exceedingly sensitive,
responding with remarkable quickness to stimulation. When two or three
minims of alcohol are dropped into a pint of water in which one of these
creatures is swimming, the pulsing of the nectocalyx is notably
increased in frequency and volume.
Romanes determined that the centres governing pulsation were located in
the nerve-ring of the swimming-bell, and that each section of the
nectocalyx had its individual nerve-centre.[4]
[4] _Jelly-Fish_, _Star-Fish_, _and Sea-Urchins_, p. 65 _et seq._
The pulsing of the nectocalyx occasions a flow of water into and out of
the bell. This current brings both food and air (oxygen) to the animal,
which is enabled to take these necessary life-sustainers into its system
through the agency of vegetative nerve-action, a phase of the
unconscious mind.
The unconscious mind made its appearance in animal life many thousands
of years before the conscious mind came into existence. The latter
psychical manifestation had its origin in sensual perception, which, in
turn, gave rise to mental recepts and concepts.
In order fully to understand the origin of mind, it will be necessary to
investigate the senses as they are observed in the lower animals. The
first manifestation of conscious mind, which is, as I believe, conscious
determination, or, volitional effort, is directly traceable to stimuli
affecting the senses. This primal operation of conscious mind, and the
manner in which it is developed from sensational perceptions, will now
be discussed.
CHAPTER I
THE SENSES IN THE LOWER ANIMALS
I am inclined to believe that the primal, fundamental sense,--the sense
of touch,--from which all the other senses have been evolved or
developed, has been in existence almost as long as life.
It is quite probable that it is to be found in the very lowest animal
organisms; and, if our own senses were acute enough, it is more than
probable that we would be able to demonstrate its presence, beyond
peradventure, in such organisms.
The senses of taste and smell, according to Graber, Lubbock, Farre, and
many other investigators, seem to be almost as old as the sense of
touch. My own observations teach me that certain actinophryans,[5]
minute, microscopic animalcules, can differentiate between the starch
spores of algæ and grains of sand, thus showing that they possess taste,
or an analogous sense.
[5] Vide the writer, _N. Y. Medical Record_, August 15, 1896.
On one occasion I was examining an actinophrys (_Actinophrys
Eichornii_), which was engaged in feeding. It would seize a rotifer
(there were numerous _Brachioni_ in the water) with one of its
pseudopodia, which it would then retract, until the captured Brachionus
was safely within its abdominal cavity. On the slide there were several
grains of sand, but these the actinophrys passed by without notice.
I thought, at first, that this creature's attention was directed to its
prey by the movements of the latter, but further investigation showed me
that this was not the case.
After carefully rinsing the slide, I placed some alga spores (some of
which were ruptured, thus allowing the starch grains to escape) and some
minute crystals of uric acid upon it. Whenever the actinophrys touched a
starch grain with a pseudopod, the latter was at once retracted,
carrying the starch grain with it into the abdominal cavity of the
actinophryan; the uric acid crystals were always ignored.
I conclude from this experiment, that the actinophrys, which is
exceedingly low in the scale of animal life, recognizes food by taste,
or by some sense analogous to taste.
Many species of these little animals, however, are not as intelligent as
the Eichorn actinophrys; they very frequently take in inert and useless
substances, which, after a time, they get rid of by a process the
reverse of that which they use in "swallowing." By the latter process
they put _themselves_ on the outside of an object--in fact, they
surround it; by the former, they put the _object_ outside by allowing
it to escape through their bodies.
The sense of sight makes its appearance in animals quite low in the
scale, therefore the reader will pardon me if, while discussing this
sense, I prove to be a bit discursive. The subject is, withal, so very
interesting that it calls for a close and minute investigation.
One of the immutable laws of nature declares that animals which are
placed in new surroundings, not fatal to life, undergo certain changes
and modifications in their anatomical and physiological structures to
meet the exigencies demanded by such a modification of surroundings.
Thus, the flounder and his congeners, the turbot, the plaice, the sole,
etc., were, centuries and centuries ago, two-sided fishes, swimming
upright, after the manner of the perch, the bass, and the salmon, with
eyes arranged one on each side of the head. From upright fishes,
swimming, probably, close to the surface of the sea, they became
dwellers on its bottom, and, in order to hide themselves more
effectually from their enemies or their prey, they acquired the habit of
swimming with one side next to the ground, and of partially or wholly
burying themselves in the mud, always, however, with one side down. They
thus became flat fishes, losing the coloring of their under surfaces,
and their eyes migrating across their foreheads and taking up positions
on the upper surfaces of their heads. Again, when animals are placed
among surroundings in which there is no need for some special organ,
this organ degenerates, and passes wholly or partially into a
rudimentary condition, or, entirely out of existence. These latter
effects of changed conditions on animals are especially noticeable in
the effect of continual darkness on the organs of sight of those
creatures which, owing to said mutations, have been compelled to dwell
in darkness for untold ages.
The mole, far back in the past, had eyes, and gained its livelihood
above ground in the broad light of day; but, owing to some change in its
surroundings, it was forced to burrow beneath the surface of the earth;
consequently its organs of sight have degenerated, and are now
practically worthless as far as _vision_ is concerned. All moles,
however, can tell darkness from light, consequently, are not wholly
blind--a certain amount of _sight_ remains. This is due to the fact
that, although the optic nerve, on examination, is invariably found to
be atrophied or wasted, there yet remain in the shrivelled nerve-cord
true nerve-cells; these nerve-cells transmit light impressions to the
brain.
Even if the optic nerves, and, in fact, all of the structures of the
eye, were absent, I yet believe that the mole could differentiate
between daylight and darkness. The sensitive tufts and filaments of
nerve in the skin, undoubtedly, in many instances, respond to the
stimulation of light, so that totally blind animals, animals with no
rudimentary organs of vision whatever, and the inception of whose
ancestors, themselves wholly blind, probably took place thousands of
years ago, show by their actions that light is exceedingly unpleasant to
them. Thus, I have seen actinophryans taken from the River Styx in
Mammoth Cave (which is their natural habitat), seeking to hide
themselves beneath a grain of sand which happened to be drawn up in the
pipette and dropped upon the glass slide beneath the object-glass of my
microscope.
I have repeatedly seen the blind fish of Mammoth Cave seeking out the
darkest spots in aquaria. In point of fact, I think it can be
demonstrated that light is directly fatal to these fishes; they soon die
when taken from the river and placed in aquaria where there is an
abundance of light.
These fish, although they have rudimentary eyes, never have the
slightest remaining trace of nerve-cells in the wasted optic nerve (that
is, I have never been able to discover any), thus showing that their
appreciation of light is not derived through the agency of their eyes.
An eyeless spider (_Anthrobia_) taken from the same cavern showed a like
distaste for light, and yet, in this insect, there is absolutely no
vestige of an eye or its nerves.
Finally, a friend of mine, a youth of eighteen, totally blind since
birth, can differentiate between daylight and darkness. On one occasion
I carefully blindfolded him and led him into the well-lighted office of
a brewery (he had never been in a brewery before), and asked him if it
were light or dark. He answered that it was almost as light as day. I
then conducted him into the dark beer vaults, and as soon as he passed
the door he exclaimed, "How cold and dark it is here!" Thinking that he
might possibly associate darkness with coldness, I asked him if this
were the case. "No," he replied, "I _see_ the darkness and I _feel_ the
cold; they are not the same."
In these animals--and I include man--continuous darkness has modified
sensibility (sense of touch) to such an extent that it has partially
taken on the functions of the useless organs--the eyes; these creatures
_see_ with their skins.
I do not believe that there is a creature in existence to-day, whether
it has eyes or not, which cannot tell the difference between night and
day. Professor Semper says that in the Pelew Islands he found a small
fresh-water creature, whose generic name is _Cymothoe_, in pools where
daylight penetrated, that was absolutely blind.[6] We have fresh-water
Cymothoe living in our own waters that are close kin to the Pelew
islander mentioned by Semper, and which are not blind. Along the middle
of their backs, over the edge of each segment, there is an oblong dark
spot. This little collection of coloring-matter is covered by a
transparent membrane, the cornea, and has a special nerve leading to the
brain, if I may use the word. These spots are primitive eyes, the
analogues of which are preserved by many of the true worms. I am
inclined to believe that Semper would find primitive eyes of some form
or other in the Cymothoe he mentions, if he were again to examine it.
The insects, etc., which dwell in caves, and which have eyes, are new
arrivals; they have not dwelt long enough in total darkness to have
experienced the full effects of changed surroundings. They show,
however, that they are beginning to feel such effects, for there is more
or less diminution in the color-cells of the eyes and body coverings. My
experiments on fish and frogs show, conclusively, that the
color-producing function is directly due to light stimulation. The
longer fish and frogs are kept in total darkness, the lower is the
number of color-cells and the smaller is the amount of coloring-matter.
This accounts for the fact that all animals which have dwelt in darkness
for untold ages are absolutely colorless. Pigmented or colored fishes,
nevertheless, having well-developed organs of vision, have been taken
from such depths (over a mile) as to preclude the possibility of a
single ray of daylight.[7] These fishes, however, are phosphorescent,
and thus furnish their own light. Moreover, I am inclined to believe
that the vast depths of the ocean, in certain localities, lie bathed in
a continuous phosphorescent glow, so that creatures living there neither
lose their color nor their eyes, sufficient light being present to
prevent degeneration. Where eyeless and colorless fishes are brought up
from great depths, there the ocean is not phosphorescent, but is in
absolute darkness.
[6] Semper, _Animal Life_, p. 83.
[7] Hickson, _The Fauna of the Deep Sea_, p. 150 _et seq._
The preceding observations indicate that the sense of sight is a very
old sense, and that it is to be found in a primitive form (ocelli) in
animals of exceedingly low organization. That this is true, I will now
attempt to demonstrate.
Sight is the result of the conversion of one form of motion into
another--a conservation, as it were, of energy. Thus, waves of light
coming from a luminous body are arrested by the pigment-cells of the
retina in our eyes and are transmuted into another form of motion, which
is called nerve energy (in this instance, sight). It would seem that as
far as sight (_vision_ is not included) is concerned, eyes of very
simple construction would amply satisfy the needs of thousands of
creatures whose existence does not depend upon vision. This supposition
is undoubtedly correct; there are many creatures in existence to-day
with eyes so exceedingly simple that they can form no visual picture of
objects--they are only able to discriminate between light and darkness.
Primitive eyes appear in animals very low in the scale of life; probably
the most remarkable of these early organs of sight are to be found in
the medusa, or jelly-fish. This creature, with its bell-shaped body and
pendent stem, bears a striking resemblance to an umbrella; noting this
resemblance, naturalists have given the name _manubrium_, "handle," to
the stem. Around the edge of the umbrella, and situated at regular
intervals, are certain round, cell-like organs, which vary considerably
in number. Some species have only eight, while others have sixty,
eighty, and even (in OEquorea) as high as six hundred.[8] These
so-called "marginal bodies" are the eyes of the jelly-fish. By many
biologists these organs are considered to be ears; they contain within
their capsules transparent bodies, which some scientists deem otoliths,
or "hearing-stones." Experimentation and microscopical examinations,
however, have taught me very recently to believe otherwise. In these
marginal bodies there is always a deposit of pigment; this is,
unquestionably, a primitive retina, while the transparent disk is,
indubitably, a primitive lens. That these creatures can tell the
difference between light and darkness is a fact easily demonstrated.
Time and again have I made them follow a bright light around the wall of
the aquarium in which they were confined. On one occasion I made some
medusæ tipsy, and their drunken gravity as they rolled and staggered
through the water in pursuit of the light was as sorrowful as it was
instructive; their actions in this respect were those of intoxicated
men. After I had siphoned off the alcoholized water and replaced it with
pure, they rapidly regained their normal status; whether or not any of
them felt any evil effects from their involuntary debauch, I am not
prepared to state.
[8] Lubbock, _Senses, Instincts, and Intelligence of Animals_, p. 84.
The eyes of sea-urchins are rather highly developed, having corneæ,
retinæ, and lenses. The lens generally lies in a mass of pigment, and,
as Lubbock remarks, looks like a brilliant egg in a scarlet nest.[9] The
eyes are scattered over the dorsal surface of the creature's body, and
are commonly situated just beneath the skin; they are, however,
sometimes elevated on pear-shaped bulbs. The eyes of starfish are
generally quite primitive in character, as far as I have been able to
determine, being simply pigmented spots which are supplied with nerves;
in several species, however, I have been able to make out lenses. The
eyes are arranged along the rays or arms, and vary in number.
[9] "In Solaster or Asteracanthion the lenses look like brilliant
eggs, each in its own scarlet nest."--LUBBOCK, _Senses, Instincts, and
Intelligence of Animals_, p. 132 _et seq._
Even the stay-at-home and humble oyster has eyes (not the round, fleshy
muscle called the "eye" by gourmands and epicures, but bright spots
around the edge of the mantle)--primitive eyes, it is true, yet amply
sufficient for the needs of a domestic, non-travelling, home body like
the oyster.
In most of the worms the eyes are simple ocelli--spots of pigment
supplied with nerves. These eyes can discriminate between light and
darkness, which is all that is required of them; but in the Alciope, a
small sea-worm, these organs are brought to a high degree of perfection.
This worm is exceedingly transparent, so that when observing it, it is
difficult to make out more than its large orange eyes and the violet
segmental organs of each ring. It looks like an animated string of
violet disks surmounted by a pair of orange-colored eyeglasses. The eye
of this creature is strikingly like that of a human being; it has a
cornea, an "eye-skin," a lens, vitreous humor (posterior chamber), and
retina.
Another aquatic worm, Myrianida, is still more remarkable, not only on
account of its eyes, but also on account of the wonderful way in which
it reproduces its young. When seen swimming in the water it presents the
appearance of a long, many-ringed worm, which impels itself through and
by the aid of its hundreds of flat, oar-like legs. Closer inspection
reveals the startling fact that this seemingly single worm is really a
multiple worm--six or more individuals being joined together, thus
forming a living chain. This creature reproduces itself by
fissigemation; that is, when the young worms arrive at a certain age
they separate from the parent worm and begin life as individuals. These
in turn eventually become multiple worms and divide into individuals,
and so on _ad infinitum_. The tail worm, or that section farthest from
the head, is the oldest and is always the first to leave its comrades
and take up a separate existence. The adverb _always_ in the above
sentence is, strictly speaking, not exactly accurate, for on one
occasion I saw the separation occur at the second head from the tail,
thus producing twins. The two sections came apart, however, in a very
few seconds after their departure from the colony. I am inclined to
believe that this deviation from the normal was due to accident;
probably to manipulation. This annelid is really "many in one" until the
very moment of division; the alimentary canal, nerves, blood-vessels,
etc., extend in unbroken continuity from the head of the parent worm to
the tail of the last section. In every fourth (sometimes fifth) ring two
round, dark-colored spots will be observed; these spots are ocelli, and
some of them eventually become the eyes of young worms. These organs
even in their embryonic state possess sight, for they have special
nerves and pigment-cells; they can differentiate between light and
darkness.
The snail carries its eyes in telescopic watch-towers. This animal is,
for the most part, nocturnal in its habits, and, since prominent and
commanding view points are assigned to its organs of sight, one would
naturally expect to find a comparatively high degree of development in
them; and this supposition is correct. The eyes of the creature are in
the extreme tips of its "horns," and consist of (1) a cornea, (2) a
lens, and (3) a retina. Lubbock is rather disposed to decry the visual
powers of the snail;[10] my conclusions, drawn from personal
observations, are, however, directly the opposite. The position of the
eyes at the extreme tips of the horns naturally indicates that they
subserve a very useful purpose; otherwise they would not have attained
such prominence and such a high degree of development. Actual
experimentation declares that the garden snail can see a moving white
object, such as a ball of cotton or twine, at a distance of two feet. In
my experiments I used a pole ten feet in length, from the tip of which a
white or dark ball was suspended by a string. The ball was made to
describe a pendulum-like movement to and fro in front of the snail on a
level with the tips of its horns. Time and again I have seen a snail
draw in its horns when it perceived the white ball, to it an unknown and
terror-inspiring object. I have likewise seen it change its line of
march, and proceed in another direction, in order to avoid the
mysterious white stranger dancing athwart its pathway. Dark-colored
objects are not so readily perceived; at least, snails do not give any
evidence of having seen them until they are brought within a foot of the
creatures under observation. A snail will generally see a black ball at
twelve or fourteen inches; sometimes it will not perceive the ball,
however, until it has been brought to within six or eight inches of its
eyestalks. During the season of courtship snails easily perceive one
another at the distance of eighteen or twenty inches. I have often
watched them at such times, and have been highly entertained by their
actions. The emotional natures of snails, as far as love and affection
are concerned, seem to be highly developed, and they show plainly by
their actions, when courting, the tenderness they feel for each other.
This has been noticed by many observers of high authority, notably
Darwin, Romanes, and Wolff.[11] Mantagazza, a distinguished Italian
scientist, in his _Physiognomy and Expression_, writes as follows: "As
long as I live I shall never see anything equal to the loving tenderness
of two snails, who, having in turn launched their little stone darts (as
in prehistoric times), caress and embrace each other with a grace that
might arouse the envy of the most refined epicurean."[12]
[10] Lubbock, _loc. cit. ante_, p. 140.
[11] Romanes, _Animal Intelligence_, p. 27.
[12] Mantagazza, _loc. cit._, p. 97.
Darwin tells us that two snails, one of them an invalid, the other in
perfect health, lived in the garden of one of his friends. Becoming
dissatisfied with their surroundings, the healthy one went in search of
another home. When it had found it, it returned and assisted its sick
comrade to go thither, evincing toward it, throughout the entire
journey, the utmost tenderness and solicitude.[13] The healthy snail
must have used its sight, as well as its other senses, to some purpose,
for, if my memory serves me correctly, we are told that the sick snail
rapidly regained its health amid its new surroundings.
[13] Darwin, _Descent of Man_, pp. 262, 263.
The crayfish also has its eyes at the tips of eyestalks, but the eyes of
this creature are very different, indeed, from the eyes of the snail.
They are what are known as compound eyes, a type common to the crayfish
and lobster families. Viewed from above, the cornea of a crayfish is
seen to be divided into a number of compartments or cells, and looks, in
this respect, very much like a section of honeycomb. The microscope
shows that in each one of these cell-like compartments there is a
transparent cone-shaped body; this is called the crystalline cone. The
apex of this cone is prolonged into an exceedingly small tube, that
enters a striped spindle-like body called the striated spindle; the
entire structure is called a visual rod. Nerve-fibrils emanating from
the optic nerve enter the striated spindle at its lower extremity, and
in this way nervously energize the visual rod. There is a deposit of
pigment about the visual rod which arrests all rays of light save those
which strike the cornea parallel to the long axis of the crystalline
cone. We see from this that the visual picture formed by a crayfish's
eye must be made up of many parts; it is, in fact, a mosaic of hundreds
of little pictured sections, which, when united, form the picture as a
whole. Each visual rod receives its impression from the ray or rays of
light reflected from the object viewed which strike it in the line of
its long axis; the other rays are stopped by the layer of pigment-cells.
When the impressions of all the visual rods are added together, the sum
will be a mosaic of the object, but such a perfect one that the junction
of its many portions will be absolutely imperceptible.
The crayfish can see quite well. It has been thought that this creature
uses its sense of smell more than its sense of sight in the procurement
of its food. This is undoubtedly true where the animal is surrounded by
water that is muddy, or that is otherwise rendered opaque. The
odoriferous particles coming from the food being carried to the creature
by the water, it follows them until it arrives at this source.
It is different, however, in clear water and on land. I have seen
crayfish rush down stream after bits of meat thrown to them, thus showing
that here, at least, the sense of sight directed them. Again, I have
enticed crayfish from clear streams by slowly dragging a baited hook in
front of them. Moreover, when high and dry on land, I have seen them
follow with their eyes and bodies the tempting morsel as it waved to and
fro in the air above their heads.
The female crayfish carries her eggs beneath her tail, and, when they
have hatched out, the young find this sheltering member a safe and cosey
dwelling-place until they have grown strong enough to enter life's
struggle. At such times, the mother crayfish is quite brave, and will do
battle with any foe. With her eyestalks protruded to their utmost extent,
she vigilantly watches her enemy. Her eyes follow his movements, and her
sharp nipper is held in readiness for immediate use.
Actual experimentation has taught that these animals can descry a man at
the distance of twenty or twenty-five feet. When approaching a crayfish
"town" for the purpose of making observations, I use the utmost caution;
otherwise, each inhabitant will retreat into its burrow before I can
come close enough to observe them, even with my field-glasses.
The gyrinus, or "whirligig beetle," whose dwelling-place during the
greater portion of its life is, like that of the crayfish, in ponds and
streams, has remarkably acute vision. This insect is a true cosmopolite,
however, and is as much at home on dry land as it is in the water. All
seasons seem to be alike to it, just so the sun shines; for, during the
hottest days of summer and the coldest days of winter (that is, if there
is sunlight and no ice on the water), it may be seen on the surface of
ponds and streams, gyrating hither and thither in a seemingly mad and
purposeless manner.
Several of these creatures will be seen at one moment floating on the
water, still and motionless; the next moment they will be darting here
and there over the surface of the water, their black and burnished backs
shining in the sunlight like brilliant gems. Suddenly, it is "heels up
and heads down," and they disappear beneath the surface, each of them
carrying a bubble of air caught beneath the wing-tips; or, as the late
William Hamilton Gibson expresses it, "they carry a brilliant lantern
that goes gleaming like a silver streak down into the depths, for a
bubble of air is caught beneath their black wing-covers, and a diamond
of pure sunlight accompanies their course down among the weeds until
they once more ascend to the surface."[14] This little beetle is well
provided with eyes, for it has a large pair beneath its head, with which
it sees all that is going on in the water below, and another pair on the
sides of its head, with which it keeps a bright lookout above. That it
has remarkably keen vision with the latter pair, any one who has tried
to steal upon them unawares can testify.[15]
[14] William Hamilton Gibson, _Sharp Eyes_, p. 307.
[15] I have a distinct purpose in introducing these and other
queer-eyed individuals while discussing the sense of sight. I wish to
demonstrate through one or more of them the correlation of morphology,
physiology, and psychology, as formulated in the first chapter of this
work. This is one of the most important facts in the doctrine of
evolution, and upon it is based the law of progressive psychical
development from the simple manifestations of conscious determination
in the lowest organisms to the most complex operations of the mind in
man.
The queerest of all queer-eyed animals is, probably, the Periophthalmus,
a fish inhabiting the coasts of China, Japan, India, the Malayan
Archipelago, and East Africa.[16]
[16] Semper, _Animal Life_, p. 374 _et seq._
I use the word coasts advisedly, for this strange creature when in
pursuit of its prey leaves the sea and comes out on the sands, thus
existing, for the greater portion of its life, in an element which,
according to the general nature of things, ought to be fatal to it. The
laws of evolution have, however, eminently prepared it for its peculiar
mode of life, for its gill-cavities have become so enlarged that when it
abandons the sea it carries in them a great quantity of water which
yields up the necessary supply of oxygen.
Its locomotion has been provided for likewise, for continued use along
certain lines has so developed its pectoral fins that the creature uses
them as legs, and jumps along at a surprising rate of speed.
Its eyes are very large and prominent, and possess, for a fish, the
peculiar faculty of looking around on all sides, hence its name,
"periophthalmus," which is derived from the Greek words, [Greek: peri],
around, and [Greek: ophthalmos], eye. These eyes are situated on top of
the animal's head, and present a very grotesque appearance.
The favorite food of this fish is Onchidium, a naked mollusk. And, in
the matter of eyes, this last-mentioned creature is itself worthy of
remark. Its cephalic, or head, eyes are like those of other mollusks of
its genus, and are not worthy of special mention, but its dorsal eyes,
sometimes several dozen in number, are truly remarkable. These eyes,
although they are very simple in structure, in type are the same as
those of vertebrates, having corneæ, lenses, retinæ, and "blind spots."
(In the vertebrate eye, the spot where the optic nerve pierces the
external layer of the retina is not sensitive to light impressions;
hence, it is called the "blind spot.")
When this mollusk sees periophthalmus bounding over the sands (and that
it does see is beyond all question), what does it do? It contracts a
thousand or so of little bladder-like cells in the skin of its back,
thereby discharging a hailstorm of minute concretions in the face of its
enemy. The fish, terrified and amazed by the volley, often turns aside,
and the mollusk is saved. Thus we see that its dorsal eyes are of great
service to onchidium.
The Greeks were, unwittingly, very near an anatomical truth when they
ascribed to certain monsters, called cyclopes, only one eye apiece,
which was placed in the centre of their foreheads. The cyclopean eye
exists to-day in the brains of men in a rudimentary form, for in the
pineal gland we find the last vestiges of that which was once a third
eye, and which looked out into the world, if not from the centre of the
forehead, at least from very near that point. There is alive to-day a
little creature which would put to shame the one-eyed arrogance and
pride of Polyphemus, and Arges, and Brontes, and Steropes, and all the
rest of the single-eyed gentry who, in the days of myths and
myth-makers, inhabited the "fair Sicilian Isle." The animal in question
is a small lizard, called Calotis. Its well-developed third eye is
situated in the top of its head, and can be easily seen through the
modified and transparent scale which serves it as a cornea. Many other
lacertilians have this third eye, though it is not so highly organized
as it is in the species just mentioned. A tree lizard, which is to be
found in the mountains of East Tennessee and Kentucky, has its third eye
quite well developed. This little animal is called the "singing
scorpion" by the mountaineers (by the way, all lizards are scorpions to
these people), and is a most interesting creature. I heard its plaintive
"peep, peep, peep," on Chilhowee Mountain a number of times before I
became aware of the fact that a lizard was the singer. On dissection,
the third eye will be found lying immediately beneath the skin; it has a
lens, retina, and optic nerve.
Thus we see that the sense of sight is to be found in animals very low
in the scale of life. From a simple accumulation of pigment-cells which
serves to arrest light rays (in simple organisms such as rotifers) to
that complex and beautiful structure--the human eye--the organs of
vision have been developed, step by step.
We will also see in the course of this discussion that, just as these
simple and primal organisms have given place to more complex forms, just
so have the operations of mind become higher and more involved. We see,
in periopthalmus, a creature exceedingly well adapted by form, function,
and intelligence to its manner of life. We must admit, in fact, the
correlation and interdependence of morphology, physiology, and
psychology in the evolution of this creature from its ancestral form to
its present status.
The primitive organ of audition as it is to be observed in creatures of
simple, comparatively speaking, organization is as simple as is the
anatomy of the animals in which it is found. Commonly, it is a hollow
hair, which is connected by a minute nerve-filament with the sensorium.
Sound vibrations set the hair to vibrating, which in turn conveys the
vibrations to the nerve-filament, and so on to the auditory centre.
Sometimes the hair is not hollow; in this case, the root of the hair is
intimately associated with nerve-filaments which take up vibrations.
It is highly probable that the majority of the lower animals, especially
those which are sound-producers, can hear just as we hear. It is also
highly probable that the so-called deaf animals can hear, just as we
hear when we have either been born deaf, or through disease have lost
the power of hearing--by _feeling_ the sound waves.
Owing to our own lack of acuteness, all of the problems involved in this
question of audition in the lower animals will, probably, never be
definitely settled; yet, reasoning by analogy, we can, approximately,
solve some of them.
By far the larger number of entomologists locate the auditory organs of
insects in their antennæ. I have only to mention the names of such men
as Kirby, Spence, Burmeister, Hicks, Wolff, Newport, Oken, Strauss,
Durkheim, and Carus, who advance this opinion, to show what a formidable
array of talent maintains it. Yet my observations lead me to believe
otherwise, though these authorities are in part correct. As far as
Lepidoptera are concerned, and certain of Hemiptera, they are right--the
antennæ in these creatures are the seat of the organs of audition. But
in Orthoptera, in most of Coleoptera, Hymenoptera, and Diptera, and in
certain bugs (Hemiptera), they are located elsewhere. The habit that
almost all insects have of retracting their antennæ when alarmed by
noise, or otherwise, has done much to advance and strengthen the opinion
that these appendages are the seat of insect ears; yet I am confident
that in nine cases out of ten the antennæ are retracted through fear of
injury to them, and not through any impression made on them by sound.
The antennæ are the most exposed and least protected of any of the
appendages or members of the insect body; hence their retraction by
insects when alarmed is an instinctively protective action. They shelter
them as much as possible in order to keep them from being injured.
Again, although the antennæ of most insects are provided with numerous
sensitive hairs, or setæ, we have no right to assume that these hairs
are auditory; no "auditory rods," otoliths, etc., are to be found
generally in antennæ, yet there are exceptional instances. Leydig found
auditory rods in the antennæ of _Dyticus marginalis_ (Furneaux[17]), the
giant water-beetle, and I myself have observed them in _Corydalis
cornuta_ and other neuropterous insects. I am inclined to believe that
the entire order of Neuroptera has antennal ears, and should therefore
in this respect be classed with Lepidoptera.
[17] Consult Furneaux, _Life in Ponds and Streams_, p. 325.
In grasshoppers and crickets the ears are situated in the anterior pairs
of legs. If the tibia of a grasshopper's anterior leg be examined, two
(one before and one behind) shining, oval, membranous disks, surrounded
by a marginal ridge, will be at once observed. These are the tympana or
ear-drums of the ear of that leg. Where the trachea, or air-tube, enters
the tibia it becomes enlarged and divides into two channels; these two
channels unite again lower down in the shaft of the tibia. The tracheæ
of non-stridulating grylli are much smaller than those of
sound-producing grasshoppers. The same may be said of the tibial
air-tubes of the so-called dumb crickets. In grasshoppers and crickets
the ear-drums lie bathed in air on both sides--the open air on the
external side and the air of the air-tube, or trachea, on the inside.
Lubbock calls attention to the fact that "the trachea acts like the
Eustachian tube in our own ear; it maintains an equilibrium of pressure
on each side of the tympanum, and enables it freely to transmit
atmospheric vibrations."
In grasshoppers the auditory nerve, after entering the tibia, divides into
two branches, one forming the supratympanal ganglion, the other descending
to the tympanum and forming a ganglion known as Siebold's organ. This
last-mentioned ganglion is strikingly like the organ of Corti in our own
ear, and undoubtedly serves a like purpose in the phenomenon of audition.
The organ of Corti is composed of some four thousand delicate vesicles,
graduated in size, each one of which vibrates in unison with some
particular number of sound vibrations. The organ of Siebold in the
grasshopper's ear begins with vesicles, of which a few of the first are
nearly equal in size; these vesicles then regularly diminish in size to
the end of the series. Each of these vesicles contains an auditory rod,
and is in communication with the auditory nerve through a delicate
nerve-fibril. I have observed that each of these nerve-fibrils swells into
a minute ganglion immediately after leaving its particular vesicle; the
function of these ganglia is, I take it, to strengthen and reënforce
nerve-energy. No other observer mentions these ganglia, as far as I have
been able to determine; they may have been absent, however, in the
specimens studied by others, yet in the specimens studied by myself--the
"red-legged locust" (_Melanoplus femur-rubrum_, Comstock)[18] and the
"meadow grasshopper" (_Xiphidium_), they were always present.
[18] Consult Comstock, _Manual for the Study of Insects_, p. 110.
That grasshoppers, locusts, and crickets can hear, no one who has
observed these creatures during the mating season will for one instant
deny; they hear readily and well, for in most of them the sense of
hearing is remarkably acute.
Immediately behind the wings of flies two curious knobbed organs are to
be observed; these are considered to be rudimentary hinder wings by
entomologists, and are called the halteres. Bolles Lee and others of
the French scientists call them _balanciers_. This latter name I
consider the correct one, for these organs unquestionably preside over
alate equilibrium: they are true balancers. I do not propose to enter
into any discussion as to whether these organs are rudimentary wings or
not; suffice it to say that they appear to me to be organs fully
developed and amply sufficient to serve the purposes for which they were
created. Whether or not in the process of evolution there has occurred a
change of function, is a point which will not be discussed in this
paper. As they now exist, I deem them to be auditory organs of Diptera
(flies, gnats, etc.).
The semicircular canals are, to a great extent if not entirely, the seat
of equilibration in man. Any derangement or disease of these canals
interferes with equilibration; this is well shown in Ménière's disease,
in which there is always marked disturbance of the equilibrating
function.
If the balancers of a horsefly be removed, the insect at once loses its
equilibrium; it cannot direct its flight, but plunges headlong to the
ground. The same can be said of _Chrysops niger_--in fact, of the entire
family of Tabanidæ, of the gall gnat (_Diplosis resinicola_, Comstock),
and of the March flies (_Bibionidæ_). These widely differing flies
constitute the material from which I have derived my data; I will
venture to assert, however, without fear of contradiction, that what
has been said about the flies mentioned above is equally true of all
flies.
When the knobbed end of the balancers of the horsefly (_Tabanus
atratus_, Comstock)[19] are examined with the microscope, the cuticle
will be found to be set with minute hairs or setæ; some of these hairs
penetrate both cuticle and hypoderm, are hollow, and receive into their
hollows delicate nerve-fibrils. These nerve-fibrils pass inward toward
the centre, and enter ganglia, which in turn are in immediate connection
with the great nerves of the balancers. There is but one nerve in the
insect's body that is larger than the balancer nerve, and that is the
optic nerve; hence, it is natural to infer that the balancer nerve leads
to some special sense centre. This centre in my opinion is,
unquestionably, the seat of the auditory function.
[19] Consult Comstock, _loc. cit. ante_, p. 455.
It has been demonstrated beyond doubt that analogous hollow hairs, or
setæ, are prominent factors of audition in many animals, notably
crustaceans, such as the lobster, the crab, and the crayfish, and many
of the insect family; hence, it is logically correct to conclude that
the hollow hairs on the balancers of flies are likewise auditory hairs.
Moreover, there are grouped about the bases of these knobbed organs
certain rows of vesicles, which contain auditory rods almost identical
in appearance with the auditory rods of the grasshopper. Indeed, I have
found those in the upper row of vesicles to be precisely similar in
appearance to the rods found in Melanoplus.
I have determined that in the horsefly (_Tabanus atratus_) there are six
rows of these vesicles, and that they are graduated in size. There are
in the knobs of the balancers minute spiracles (I do not think that
these have been pointed out before by any other observer) through which
air passes into the large, vesicular cells which make up the greater
portion of the knobs; spiracles are also to be found in the shafts of
the balancers, thus providing an abundance of air to the internal
structures of these organs and allowing for the free transmission of
sound vibrations.
I am well aware of the fact that in considering these organs to be the
ears of flies, I antagonize Lee and others who consider them olfactory
in character.[20] The position I take in regard to these organs is,
however, a tenable one, and one that cannot easily be overthrown.
[20] Bolles Lee, _Les Balanciers des Dipteres_; quoted also by
Lubbock, _Senses, Instincts_, etc., pp. 110, 111.
The ears of Lepidoptera (butterflies) are situated in their antennæ. This
fact has been clearly demonstrated by Lubbock, Graber, Leydig, and Wolff.
Newport has made an especially exhaustive study of the antennæ of insects;
and he, too, places the organs of audition in these appendages.[21] But in
Coleoptera my experiments and microscopical researches compel me to
assert that I differ somewhat from the conclusions of the above-mentioned
authorities. These gentlemen locate the ears of beetles also in their
antennæ. Lubbock bases his conclusions on an experiment of Will--an
experiment which, if it had been carried a little further, would have
demonstrated the fact that the ears of beetles are not in their antennæ,
but are, on the contrary, in their maxillary palpi.
[21] Newport, _The Antennæ of Insects_, Entomol. Society, Vol. II.
Will put a female Cerambyx beetle into a box, which he placed on a
table; he then put a male Cerambyx on the table, some four inches from
the box. When he touched the female she began to chirrup, whereupon the
male turned his antennæ toward the box, "as if to determine from which
direction the sound came, and then marched straight toward the female."
Will concluded from this that the ears of the beetle were located in its
antennæ.[22]
[22] Will, _Das Geschmacksorgen der Insecten_, Wiss. Zool.; quoted
also by Lubbock, _Senses, Instincts_, etc., p. 96.
Seeing that Will's experiment as described by him was incomplete, I took
a pair of beetles belonging to the same family (genus _Prionus_), and
determined the true location of their ears by a system of rigid
exclusion. These beetles, when irritated, make a squeaking chirrup by
rubbing together the prothorax and mesothorax.
When I irritated the female she began to chirrup, and the male
immediately turned toward the small paper box in which she was confined.
I then removed the antennæ of the male, and again made the female
stridulate; the male heard her, and at once crawled toward her, although
his antennæ were entirely removed.
This showed conclusively that the organs of audition were not located in
the antennæ, as Will supposed and as Lubbock advocates. I then removed
the maxillary palpi of the male, after which the insect remained deaf to
all sounds emanating from the female.
Again, I took an unmutilated male, which at once turned and crawled
toward the chirruping female. I then removed its labial palpi, leaving
maxillary palpi and antennæ intact; it heard the female and made toward
her. The maxillary palpi were then removed (the antennæ being left _in
situ_), and at once the creature became deaf.
If the maxillary palpi of long-horned beetles be examined, certain
vesicular organs, each containing a microscopic hair, will be observed
in the basal segments; these, I take it, are auditory vesicles. In some
of the Coleoptera I have found auditory rods in the apical segments,
though this is by no means a common occurrence. In Cicindelidæ and
Carabidæ these auditory vesicles are exceedingly small, and require a
very high-power objective in order to be clearly seen.
In justice to other observers I must say, however, that I am inclined to
believe that in all beetles the antennæ in some way aid or assist
audition, but they are adjuncts, as it were, and not absolutely
necessary. It is a matter of easy demonstration to show that some of
these insects hear less acutely where they are deprived of their antennæ.
I presume they are about as necessary in audition as are the external
appendages of the human ear; this, however, is mere supposition, and has
no scientific warrant for its verity.
I have purposely said but very little about the senses of touch, taste,
and smell in this discussion of the senses in the lower animals. These
three senses have been so exhaustively treated by Lubbock in his
_Senses, Instincts, and Intelligences of Animals_, that I could not hope
to introduce any new data in regard to them. Graber, Frey, Leuckart,
Farre, Hertwig, and a host of others have likewise investigated these
senses most thoroughly.
As to the senses of sight and hearing, the matter presented a different
aspect. I was confident that I could add somewhat to the knowledge
already formulated, consequently I have treated these senses at some
length. Technicalities and the details of microscopic investigation,
especially microscopic anatomy, have been omitted; they have no place in
a work like this.