The Outline of Science, Vol. 1 (of 4)

J >> J. Arthur Thomson >> The Outline of Science, Vol. 1 (of 4)

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The Stickleback's Nest

The three-spined and two-spined sticklebacks live equally well in fresh
or salt water; the larger fifteen-spined stickleback is entirely marine.
In all three species the male fish makes a nest, in fresh or brackish
water in the first two cases, in shore-pools in the third case. The
little species use the leaves and stems of water-plants; the larger
species use seaweed and zoophyte. The leaves or fronds are entangled
together and fastened by glue-like threads, secreted, strange to say, by
the kidneys. It is just as if a temporary diseased condition had been
regularised and turned to good purpose. Going through the nest several
times, the male makes a little room in the middle. Partly by coercion
and partly by coaxing he induces a female--first one and then
another--to pass through the nest with two doors, depositing eggs during
her short sojourn. The females go their way, and the male mounts guard
over the nest. He drives off intruding fishes much bigger than himself.
When the young are hatched, the male has for a time much to do, keeping
his charges within bounds until they are able to move about with
agility. It seems that sticklebacks are short-lived fishes, probably
breeding only once; and it is reasonable to suppose that their success
as a race depends to some extent on the paternal care. Now if we could
believe that the nesting behaviour had appeared suddenly in its present
form, we should be inclined to credit the fish with considerable mental
ability. But we are less likely to be so generous if we reflect that the
routine has been in all likelihood the outcome of a long racial process
of slight improvements and critical testings. The secretion of the glue
probably came about as a pathological variation; its utilisation was
perhaps discovered by accident; the types that had wit enough to take
advantage of this were most successful; the routine became enregistered
hereditarily. The stickleback is not so clever as it looks.

[Illustration: _Photo: Imperial War Museum._

HOMING PIGEON

A blue chequer hen, which during the War (in September of 1918) flew 22
miles in as many minutes, saving the crew of an aeroplane in
difficulties.]

[Illustration: _Photo: Imperial War Museum._

CARRIER PIGEON

Carrier pigeons were much used in the War to carry messages. The
photograph shows how the message is fixed to the carrier pigeon's leg,
in the form of light rings.]

[Illustration: _Photo: James's Press Agency._

YELLOW-CROWNED PENGUIN

Notice the flightless wings turned into flippers, which are often
flapped very vigorously. The very strong feet are also noteworthy.
Penguins are mostly confined to the Far South.]

[Illustration: _Photo: Cagcombe & Co._

PENGUINS ARE "A PECULIAR PEOPLE"

Their wings have been turned into flippers for swimming in the sea and
tobogganing on snow. The penguins come back over hundreds of miles of
trackless waste to their birthplace, where they breed. When they reach
the Antarctic shore they walk with determination to a suitable site,
often at the top of a steep cliff. Some species waddle 130 steps per
minute, 6 inches per step, two-thirds of a mile per hour.]

The Mind of a Minnow

To find solid ground on which to base an appreciation of the behaviour
of fishes, it is necessary to experiment, and we may refer to Miss
Gertrude White's interesting work on American minnows and sticklebacks.
After the fishes had become quite at home in their artificial
surroundings, their lessons began. Cloth packets, one of which contained
meat and the other cotton, were suspended at opposite ends of the
aquarium. The mud-minnows did not show that they perceived either
packet, though they swam close by them; the sticklebacks were intrigued
at once. Those that went towards the packet containing meat darted
furiously upon it and pulled at it with great excitement. Those that
went towards the cotton packet turned sharply away when they were within
about two inches off. They then perceived what those at the other end
were after and joined them--a common habit amongst fishes. Although the
minnows were not interested in the tiny "bags of mystery," they were
even more alert than the sticklebacks in perceiving moving objects in or
on the water, and there is no doubt that both these shallow-water
species discover their food largely by sense of sight.

The next set of lessons had to do with colour-associations. The fishes
were fed on minced snail, chopped earthworm, fragments of liver, and the
like, and the food was given to them from the end of forceps held above
the surface of the water, so that the fishes could not be influenced by
smell. They had to leap out of the water to take the food from the
forceps. Discs of coloured cardboard were slipped over the end of the
forceps, so that what the fishes saw was a morsel of food in the centre
of a coloured disc. After a week or so of preliminary training, they
were so well accustomed to the coloured discs that the presentation of
one served as a signal for the fishes to dart to the surface and spring
out of the water. When baits of paper were substituted for the food, the
fishes continued to jump at the discs. When, however, a blue disc was
persistently used for the paper bait and a red disc for the real food,
or _vice versa_, some of the minnows learned to discriminate infallibly
between shadow and substance, both when these were presented alternately
and when they were presented simultaneously. This is not far from the
dawn of mind.

In the course of a few lessons, both minnows and sticklebacks learned to
associate particular colours with food, and other associations were also
formed. A kind of larva that a minnow could make nothing of after
repeated trials was subsequently ignored. The approach of the
experimenter or anyone else soon began to serve as a food-signal. There
can be no doubt that in the ordinary life of fishes there is a process
of forming useful associations and suppressing useless responses. Given
an inborn repertory of profitable movements that require no training,
given the power of forming associations such as those we have
illustrated, and given a considerable degree of sensory alertness along
certain lines, fishes do not require much more. And in truth they have
not got it. Moving with great freedom in three dimensions in a medium
that supports them and is very uniform and constant, able in most cases
to get plenty of food without fatiguing exertions and to dispense with
it for considerable periods if it is scarce, multiplying usually in
great abundance so that the huge infantile mortality hardly counts,
rarely dying a natural death but usually coming with their strength
unabated to a violent end, fishes hold their own in the struggle for
existence without much in the way of mental endowment. Their brain has
more to do with motion than with mentality, and they have remained at a
low psychical level.

Yet just as we should greatly misjudge our own race if we confined our
attention to everyday routine, so in our total, as distinguished from
our average, estimate of fishes, we must remember the salmon surmounting
the falls, the wary trout eluding the angler's skill, the common
mud-skipper (Periophthalmus) of many tropical shores which climbs on the
rocks and the roots of the mangrove-trees, or actively hunts small
shore-animals. We must remember the adventurous life-history of the eel
and the quaint ways in which some fishes, males especially, look after
their family. The male sea-horse puts the eggs in his breast-pocket; the
male Kurtus carries them on the top of his head; the cock-paidle or
lumpsucker guards them and aerates them in a corner of a shore-pool.

Sec. 3

The Mind of Amphibians

Towards the end of the age of the Old Red Sandstone or Devonian, a great
step in evolution was taken--the emergence of Amphibians. The earliest
representatives had fish-like characters even more marked than those
which may be discerned in the tadpoles of our frogs and toads, and there
is no doubt that amphibians sprang from a fish stock. But they made
great strides, associated in part with their attempts to get out of the
water on to dry land. From fossil forms we cannot say much in regard to
soft parts; but if we consider the living representatives of the class,
we may credit amphibians with such important acquisitions as fingers and
toes, a three-chambered heart, true ventral lungs, a drum to the ear, a
mobile tongue, and vocal cords. When animals began to be able to grasp
an object and when they began to be able to utter sufficient sounds, two
new doors were opened. Apart from insects, whose instrumental music had
probably begun before the end of the Devonian age, amphibians were the
first animals to have a voice. The primary meaning of this voice was
doubtless, as it is to-day in our frogs, a sex-call; but it was the
beginning of what was destined to play a very important part in the
evolution of the mind. In the course of ages the significance of the
voice broadened out; it became a parental call; it became an infant's
cry. Broadening still, it became a very useful means of recognition
among kindred, especially in the dark and in the intricacies of the
forest. Ages passed, and the voice rose on another turn of the
evolutionary spiral to be expressive of particular emotions beyond the
immediate circle of sex--emotions of joy and of fear, of jealousy and of
contentment. Finally, we judge, the animal--perhaps the bird was
first--began to give utterance to particular "words," indicative not
merely of emotions, but of particular things with an emotional halo,
such as "food," "enemy," "home." Long afterwards, words became _in man_
the medium of reasoned discourse. Sentences were made and judgments
expressed. But was not the beginning in the croaking of Amphibia?

Senses of Amphibians

Frogs have good eyes, and the toad's eyes are "jewels." There is
evidence of precise vision in the neat way in which a frog catches a
fly, flicking out its tongue, which is fixed in front and loose behind.
There is also experimental proof that a frog discriminates between red
and blue, or between red and white, and an interesting point is that
while our skin is sensitive to heat rays but not to light, the skin of
the frog answers back to light rays as well. Professor Yerkes
experimented with a frog which had to go through a simple labyrinth if
it wished to reach a tank of water. At the first alternative between two
paths, a red card was placed on the wrong side and a white one on the
other. When the frog had learned to take the correct path, marked by the
white card, Prof. Yerkes changed the cards. The confusion of the frog
showed how thoroughly it had learned its lesson.

We know very little in regard to sense of smell or taste in amphibians;
but the sense of hearing is well developed, more developed than might be
inferred from the indifference that frogs show to almost all sounds
except the croaking of their kindred and splashes in the water.

The toad looks almost sagacious when it is climbing up a bank, and some
of the tree-frogs are very alert; but there is very little that we dare
say about the amphibian mind. We have mentioned that frogs may learn the
secret of a simple maze, and toads sometimes make for a particular
spawning-pond from a considerable distance. But an examination of their
brains, occupying a relatively small part of the broad, flat skull,
warns us not to expect much intelligence. On the other hand, when we
take frogs along a line that is very vital to them, namely, the
discrimination of palatable and unpalatable insects, we find, by
experiment, that they are quick to learn and that they remember their
lessons for many days. Frogs sometimes deposit their eggs in very
unsuitable pools of water; but perhaps that is not quite so stupid as it
looks. The egg-laying is a matter that has been, as it were, handed over
to instinctive registration.

[Illustration: _Photo: W. S. Berridge._

HARPY-EAGLE

"Clean and dainty and proud as a Spanish Don."

It is an arboreal and cliff-loving bird, feeding chiefly on mammals,
very fierce and strong. The under parts are mostly white, with a greyish
zone on the chest. The upper parts are blackish-grey. The harpy occurs
from Mexico to Paraguay and Bolivia.]

[Illustration: _Photo: W. S. Berridge, F.Z.S._

THE DINGO OR WILD DOG OF AUSTRALIA, PERHAPS AN INDIGENOUS WILD SPECIES,
PERHAPS A DOMESTICATED DOG THAT HAS GONE WILD OR FERAL

It does much harm in destroying sheep. It is famous for its persistent
"death-feigning," for an individual has been known to allow part of its
skin to be removed, in the belief that it was dead, before betraying its
vitality.]

[Illustration: WOODPECKER, HAMMERING AT A COTTON-REEL, ATTACHED TO A
TREE

Notice how the stiff tail-feathers braced against the stem help the bird
to cling on with its toes. The original hole, in which this woodpecker
inserted nuts for the purposes of cracking the shell and extracting the
kernel, is seen towards the top of the tree. But the taker of the
photograph tied on a hollowed-out cotton-reel as a receptacle for a nut,
and it was promptly discovered and used by the bird.]

Experiments in Parental Care

It must be put to the credit of amphibians that they have made many
experiments in methods of parental care, as if they were feeling their
way to new devices. A common frog lays her clumps of eggs in the cradle
of the water, sometimes far over a thousand together; the toad winds two
long strings round and between water-weeds; and in both cases that is
all. There is no parental care, and the prolific multiplication covers
the enormous infantile mortality. This is the spawning solution of the
problem of securing the continuance of the race. But there is another
solution, that of parental care associated with an economical reduction
of the number of eggs. Thus the male of the Nurse-Frog (Alytes), not
uncommon on the Continent, fixes a string of twenty to fifty eggs to the
upper part of his hind-legs, and retires to his hole, only coming out at
night to get some food and to keep up the moisture about the eggs. In
three weeks, when the tadpoles are ready to come out, he plunges into
the pond and is freed from his living burden and his family cares. In
the case of the thoroughly aquatic Surinam Toad (Pipa), the male helps
to press the eggs, perhaps a hundred in number, on to the back of the
female, where each sinks into a pocket of skin with a little lid. By and
by fully formed young toads jump out of the pockets.

In the South American tree-frogs called Nototrema there is a pouch on
the back of the female in which the eggs develop, and it is interesting
to find that in some species what come out are ordinary tadpoles, while
in other species the young emerge as miniatures of their parents.
Strangest of all, perhaps, is the case of Darwin's Frog (Rhinoderma of
Chili), where the young, about ten to fifteen in number, develop in the
male's croaking-sacs, which become in consequence enormously distended.
Eventually the strange spectacle is seen of miniature frogs jumping out
of their father's mouth. Needless to say we are not citing these methods
of parental care as examples of intelligence; but perhaps they correct
the impression of amphibians as a rather humdrum race. Whatever be the
mental aspect of the facts, there has certainly been some kind of
experimenting, and the increase of parental care, so marked in many
amphibians, with associated reduction of the number of offspring is a
finger-post on the path of progress.

Sec. 4

The Reptilian Mind

We speak of the wisdom of the serpent; but it is not very easy to
justify the phrase. Among all the multitude of reptiles--snakes,
lizards, turtles, and crocodiles, a motley crowd--we cannot see much
more than occasional traces of intelligence. The inner life remains a
tiny rill.

No doubt many reptiles are very effective; but it is an instinctive
rather than an intelligent efficiency. The well-known "soft-shell"
tortoise of the United States swims with powerful strokes and runs so
quickly that it can hardly be overtaken. It hunts vigorously for
crayfish and insect larvae in the rivers. It buries itself in the mud
when cold weather comes. It may lie on a floating log ready to slip into
the water at a moment's notice; it may bask on a sunny bank or in the
warm shallows. Great wariness is shown in choosing times and places for
egg-laying. The mother tramps the earth down upon the buried eggs. All
is effective. Similar statements might be made in regard to scores of
other reptiles; but what we see is almost wholly of the nature of
instinctive routine, and we get little glimpse of more than efficiency
and endeavour.

In a few cases there is proof of reptiles finding their way back to
their homes from a considerable distance, and recognition of persons is
indubitable. Gilbert White remarks of his tortoise: "Whenever the good
old lady came in sight who had waited on it for more than thirty years,
it always hobbled with awkward alacrity towards its benefactress, while
to strangers it was altogether inattentive." Of definite learning there
are a few records. Thus Professor Yerkes studied a sluggish turtle of
retiring disposition, taking advantage of its strong desire to efface
itself. On the path of the darkened nest of damp grass he interposed a
simple maze in the form of a partitioned box. After wandering about
constantly for thirty-five minutes the turtle found its way through the
maze by chance. Two hours afterwards it reached the nest in fifteen
minutes; and after another interval of two hours it only required five
minutes. After the third trial, the routes became more direct, there was
less aimless wandering. The time of the twentieth trial was forty-five
seconds; that of the thirtieth, forty seconds. In the thirtieth case,
the path followed was quite direct, and so it was on the fiftieth trip,
which only required thirty-five seconds. Of course, the whole thing did
not amount to very much; but there was a definite learning, _a learning
from experience_, which has played an important part in the evolution of
animal behaviour.

Comparing reptiles with amphibians, we may recognise an increased
masterliness of behaviour and a hint of greater plasticity. The records
of observers who have made pets of reptiles suggest that the life of
feeling or emotion is growing stronger, and so do stories, if they can
be accepted, which suggest the beginning of conjugal affection.

The error must be guarded against of interpreting in terms of
intelligence what is merely the outcome of long-continued structure
adaptation. When the limbless lizard called the Slow-worm is suddenly
seized by the tail, it escapes by surrendering the appendage, which
breaks across a preformed weak plane. But this is a reflex action, not a
reflective one. It is comparable to our sudden withdrawal of our finger
from a very hot cinder. The Egg-eating African snake Dasypeltis gets the
egg of a bird into its gullet unbroken, and cuts the shell against
downward-projecting sharp points of the vertebrae. None of the precious
contents is lost and the broken "empties" are returned. It is admirable,
indeed unsurpassable; but it is not intelligent.

Sec. 5

Mind in Birds

Sight and hearing are highly developed in birds, and the senses, besides
pulling the triggers of inborn efficiencies, supply the raw materials
for intelligence. There is some truth, though not the whole truth, in
the old philosophical dictum, that there is nothing in the intellect
which was not previously in the senses. Many people have admired the
certainty and alacrity with which gulls pick up a fragment of biscuit
from the white wake of a steamer, and the incident is characteristic. In
their power of rapidly altering the focus of the eye, birds are
unsurpassed.

To the sense of sight in birds, the sense of hearing comes a good
second. A twig breaks under our feet, and out sounds the danger-call of
the bird we were trying to watch. Many young birds, like partridges,
respond when two or three hours old to the anxious warning note of the
parents, and squat motionless on the ground, though other sounds, such
as the excited clucking of a foster-mother hen, leave them indifferent.
They do not know what they are doing when they squat; they are obeying
the living hand of the past which is within them. Their behaviour is
instinctive. But the present point is the discriminating quality of the
sense of hearing; and that is corroborated by the singing of birds.
It is emotional art, expressing feelings in the medium of sound. On the
part of the females, who are supposed to listen, it betokens a
cultivated ear.

[Illustration: THE BEAVER

The beaver will gnaw through trees a foot in diameter; to save itself
more trouble than is necessary, it will stop when it has gnawed the
trunk till there is only a narrow core left, having the wit to know that
the autumn gales will do the rest.]

[Illustration: _Photo: F. R. Hinkins & Son._

THE THRUSH AT ITS ANVIL

The song-thrush takes the snail's shell in its bill, and knocks it
against a stone until it breaks, making the palatable flesh available.

Many broken shells are often found around the anvil.]

As to the other senses, touch is not highly developed except about the
bill, where it reaches a climax in birds like the wood-cock, which probe
for unseen earthworms in the soft soil. Taste seems to be poorly
developed, for most birds bolt their food, but there is sometimes an
emphatic rejection of unpalatable things, like toads and caterpillars.
Of smell in birds little is known, but it has been proved to be present
in certain cases, e.g. in some nocturnal birds of prey. It seems certain
that it is by sight, not by smell, that the eagles gather to the
carcass; but perhaps there is more smell in birds than they are usually
credited with. One would like to experiment with the oil from the preen
gland of birds to see whether the scent of this does not help in the
recognition of kin by kin at night or amid the darkness of the forest.
There may be other senses in birds, such as a sense of temperature and a
sense of balance; but no success has attended the attempts made to
demonstrate a magnetic sense, which has been impatiently postulated by
students of bird migration in order to "explain" how the birds find
their way. The big fact is that in birds there are two widely open
gateways of knowledge, the sense of sight and the sense of hearing.

Instinctive Aptitudes

Many a young water-bird, such as a coot, swims right away when it is
tumbled into water for the first time. So chicks peck without any
learning or teaching, very young ducklings catch small moths that flit
by, and young plovers lie low when the danger-signal sounds. But birds
seem strangely limited as regards many of these instinctive
capacities--limited when compared with the "little-brained" ants and
bees, which have from the first such a rich repertory of ready-made
cleverness. The limitation in birds is of great interest, for it means
that intelligence is coming to its own and is going to take up the
reins at many corners of the daily round. Professor Lloyd Morgan
observed that his chickens incubated in the laboratory had no
instinctive awareness of the significance of their mother's cluck when
she was brought outside the door. Although thirsty and willing to drink
from a moistened finger-tip, they did not instinctively recognize water,
even when they walked through a saucerful. Only when they happened to
peck their toes as they stood in the water did they appreciate water as
the stuff they wanted, and raise their bills up to the sky. Once or
twice they actually stuffed their crops with "worms" of red worsted!

Instinctive aptitudes, then, the young birds have, but these are more
limited than in ants, bees, and wasps; and the reason is to be found in
the fact that the brain is now evolving on the tack of what Sir Ray
Lankester has called "educability." Young birds _learn_ with prodigious
rapidity; the emancipation of the mind from the tyranny of hereditary
obligations has begun. Young birds make mistakes, like the red worsted
mistake, but they do not make the same mistakes often. They are able to
profit by experience in a very rapid way. We do not mean that creatures
of the little-brain type, like ants, bees, and wasps, are unable to
profit by experience or are without intelligence. There are no such
hard-and-fast lines. We mean that in the ordinary life of insects the
enregistered instinctive capacities are on the whole sufficient for the
occasion, and that intelligent educability is very slightly developed.
Nor do we mean that birds are quite emancipated from the tyranny of
engrained instinctive obligations, and can always "ring up" intelligence
in a way that is impossible for the stereotyped bee. The sight of a
pigeon brooding on an empty nest, while her two eggs lie disregarded
only a couple of inches away, is enough to show that along certain lines
birds may find it impossible to get free from the trammels of instinct.
The peculiar interest of birds is that they have many instincts and yet
a notable power of learning intelligently.

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