[Illustration: THE PLATYPUS. DRAWN BY J. W. LEWIN IN 1810.
After the original watercolour in the Mitchell Library, Sydney.]
THE PLATYPUS
ITS DISCOVERY, ZOOLOGICAL POSITION,
FORM AND CHARACTERISTICS, HABITS,
LIFE HISTORY, ETC.
BY
HARRY BURRELL, C.M.Z.S.
Co-author of
_The Wild Animals of Australasia_
_With 35 Plates_
AUSTRALIA:
ANGUS & ROBERTSON LIMITED
89 CASTLEREAGH STREET, SYDNEY
1927
Wholly set up and printed in Australia by
Eagle Press Ltd., Allen Street, Waterloo
1927
Registered by the Postmaster-General for
transmission through the post as a book
TO MY WIFE
Without whose help and encouragement this book
would probably not have been written.
PREFACE
This book is the result of nearly twenty years’ personal observation of
the platypus in its haunts, carried on while I was collecting specimens
for the University of Sydney and the Commonwealth National Museum; but
the limitations under which the work has had to be carried on, and
the impossibility of obtaining official sanction to work as a private
collector, have prevented me from exploring certain branches of the
subject and have brought my field work practically to a standstill.
Earlier observers, working without restraint, had opportunities
of discovering details which I have been debarred from studying;
nevertheless, I have not hesitated to criticize their observations
where they differ from my own, and I have ventured to suggest several
directions in which scientific investigators may proceed.
All my descriptions have been written from living specimens or from
material freshly collected; museum specimens and records have been
deliberately ignored. The illustrations also show living platypus, with
the exception of a few photographs taken from fresh carcasses; and none
of the photographs reproduced have been touched up in any way.
As the book is intended mainly for general readers, measurements have
been given in inches where possible; but for scientific purposes it has
sometimes been necessary to give them in millimetres. Roughly, 25 mm.
equal 1 inch; therefore 3 mm. equal ⅛in., 12 mm. equal ½in., etc.
H.B.
CONTENTS
PREFACE vii
I. INTRODUCTORY 1
II. DISCOVERY AND EARLY DESCRIPTIONS 16
III. CONTROVERSY ON THE ZOOLOGICAL POSITION 26
IV. CONTROVERSY ON THE LAYING OF EGGS 33
V. GENERAL CHARACTERISTICS 46
VI. NERVOUS ORGANIZATION AND SENSORY PERCEPTIONS 63
VII. THE SPUR AND CRURAL GLAND 76
VIII. THE NESTING-BURROW 105
IX. DISTRIBUTION AND HAUNTS 139
X. HABITS 147
XI. BREEDING HABITS AND LIFE HISTORY 167
XII. PRESERVATION AND ECONOMICS 193
XIII. THE PLATYPUS IN CAPTIVITY 202
BIBLIOGRAPHY 219
INDEX 223
ILLUSTRATIONS
THE PLATYPUS _Frontispiece_
THE AUTHOR 6
MRS. HARRY BURRELL FONDLING TWIN NESTLINGS 6
UPPER AND LOWER JAWS FORCED WIDE OPEN 10
SKELETON OF PLATYPUS 11
JAWBONES, SHOWING DIVIDED EXTREMITIES 14
“AN AMPHIBIOUS ANIMAL OF THE MOLE KIND” 18
MALE PLATYPUS FLOATING 18
MALE PLATYPUS WATCHING INTENTLY 30
FEMALE PLATYPUS LISTENING INTENTLY 30
VENTRAL VIEW OF MALE PLATYPUS 34
HEAD OF FEMALE PLATYPUS, SHOWING DIRECT DORSAL VISION 46
VENTRAL VIEW OF LIPS 46
PLATYPUS PAWS, EXPANDED FOR SWIMMING, AND CONTRACTED FOR
WALKING 50
FEMALE PLATYPUS SUCKLING YOUNG 54
FEMALE PLATYPUS 54
TOP OF LEFT HIND FOOT, WITH SWIMMING MEMBRANE FULLY
EXTENDED 58
SOLE OF RIGHT HIND FOOT 58
HEAD OF INFURIATED MALE PLATYPUS 62
NESTLING PLATYPUS, ABOUT FIVE WEEKS OLD 62
EXPERIMENTS ON SENSORY PERCEPTIONS OF PLATYPUS BENEATH
WATER 66
POISON GLAND CONNECTED BY DUCT TO WELL AT BASE OF SPUR 94
GENERAL VIEW OF MALE PLATYPUS 94
SOLE OF RIGHT HIND FOOT, SHOWING SPUR NORMALLY SHEATHED 98
SOLE OF LEFT HIND FOOT, SHOWING SPUR IN ACTION 98
UNEARTHING PLATYPUS, RETREAT STATION, MACDONALD RIVER,
N.S.W. 110
A NEWLY-OPENED NESTING-CAVITY 114
NEST COMPOSED OF GUM-LEAVES AND GRASS STEMS 118
BROODING FEMALE PLATYPUS 118
MODELS OF NESTING-BURROW 122, 124
NESTING-BURROW WITH TWO OPENINGS 126
VARIETY IN NESTS 126
MALE PLATYPUS (1) 130
MALE PLATYPUS (2) 130
BURROW WITH FOUR NESTS 134
PLATYPUS EGGS AND YOUNG 134
MACDONALD RIVER, N.S.W. 138
“BLUE HOLE,” NAMOI RIVER, N.S.W. 138
PLATYPUS MANOEUVRING ALONG A SANDY BOTTOM 142
MALE PLATYPUS RUNNING AT TOP SPEED (1) 146
MALE PLATYPUS RUNNING AT TOP SPEED (2) 146
VENTRAL VIEW OF MALE PLATYPUS 158
FEMALE PLATYPUS TAKEN DIRECTLY FROM NEST AND PERSUADED TO
ADOPT SLEEPING POSITION 162
TWIN EGGS IN NEST COMPOSED ENTIRELY OF REED ROOTS 174
TRIPLET NESTLINGS ABOUT FOUR DAYS OLD. NEST COMPOSED OF
GUM-LEAVES AND GRASS 174
FEMALE PLATYPUS IN NEST OF GUM-LEAVES AND GRASS 178
MILK GLAND FROM LEFT SIDE 182
BROODING FEMALE STEALTHILY GROVELLING HER WAY FROM HER NEST
WHICH HAS BEEN EXPOSED 186
TWIN NESTLINGS ABOUT FOUR WEEKS OLD, DIRECT FROM BURROW 206
NESTLING PLATYPUS, ABOUT THREE WEEKS OLD, SHOWING
“MILK-LIPS” 206
EXHIBITING A PLATYPUS IN AN EXPERIMENTAL “PLATYPUSARY,”
CONSTRUCTED IN 1910 210
PORTABLE “PLATYPUSARY,” DESIGNED FOR TRAVELLING 210
INTERIOR OF PORTABLE “PLATYPUSARY” 214
[Illustration: THE AUTHOR.]
[Illustration: MRS. HARRY BURRELL FONDLING TWIN NESTLINGS, IN CAMP.]
CHAPTER I
INTRODUCTORY
The first printed description of the platypus appeared in the tenth
volume of the _Naturalist’s Miscellany_ (1799) under the name _Platypus
anatinus_ and was written by Dr. George Shaw, of the British Museum,
where the original skin, received in 1798, is still preserved.
In 1800 the German anatomist Blumenbach received a skin from Sir
Joseph Banks (one of two sent by Governor Hunter), and described
it as _Ornithorhynchus paradoxus_. Shaw’s generic name _Platypus_
was not permissible, it having been used in 1793 by Herbst for a
genus of beetles. The correct name of the animal therefore became
_Ornithorhynchus anatinus_ Shaw; but ‘platypus’ has survived in the
vernacular, to the exclusion of ‘duck-bill’ and ‘water-mole,’ which
were in general use among the earlier colonists.
No animal has given rise to so much controversy among both laymen and
professed zoologists. The first specimens which reached England were
regarded with suspicion. Shaw’s account, quoted on page 17, shows
clearly enough his doubts and fears, which were dissolved by the
arrival of further specimens; Home’s anatomical research in 1802 put
the genuineness of these beyond all question. But the general feeling
is summed up by Knox (1823, p. 27), who writes:--
“It is well known that the specimens of this very extraordinary
animal first brought to Europe were considered by many as
impositions. They reached England by vessels which had navigated
the Indian seas, a circumstance in itself sufficient to rouse the
suspicions of the scientific naturalist, aware of the monstrous
impostures which the artful Chinese had so frequently practised on
European adventurers; in short, the scientific felt inclined to class
this rare production of nature with eastern mermaids and other works
of art; but these conjectures were immediately dispelled by an appeal
to anatomy.”
The ‘eastern mermaid’ so mentioned is still to be seen occasionally in
curiosity shops, and consists of the skin of the fore-part of a monkey
skilfully sewn to the tail-part of a fish.
The singular nature of the platypus was not, however, confined to its
external form, and the proof that its duck-like bill really belonged to
it by no means ended the troubles of contemporary zoologists. A furred
animal should obviously be a mammal--that is to say, it should have
a uterus to contain its foetal young, and milk glands with external
nipples for the suckling of the young when born.
But Home (1802) found no uterus, no mammary glands, and no nipples. Was
the platypus a mammal? Home discovered that the oviducts of the female,
instead of uniting to form a uterus as in the majority of mammals,
opened separately into a cloaca, as in birds and reptiles.
Here was material for two further controversies. Should
_Ornithorhynchus_ be included in the mammalian class, or must a new
vertebrate class be added for its inclusion? We know now that we may
fairly include the platypus and its only near relative, the echidna,
in a sub-class of the Mammalia (the Ornithodelphia), which, though so
insignificant numerically, is the equivalent, zoologically, of the
larger marsupial sub-class, Didelphia, and of the infinitely greater
sub-class Monodelphia, which comprises all other mammals. But it was
long before this point was settled. The varying opinions will be
detailed in due course.
The second controversy concerned the method of reproduction. Persistent
reports came from New South Wales that the platypus laid eggs, but
definite evidence was lacking. Sir John Jamison, writing from Sydney
on March 18, 1817 (Jamison, 1818, p. 585) states categorically:--“The
female is oviparous, and lives in burrows in the ground.” But he
offers no proof. Lesson (1839, p. 302) writes:--
“It is in New South Wales that one meets those singular and fantastic
creatures to which naturalists have not been able to assign a
position: the _ornithorhynchuses_ or _paradoxals_ with a duck’s
beak, which live in the waters of the rivers, and which lay eggs,
creatures set across the path of the scientific method to show its
worthlessness.”
These statements were not, however, acceptable to European zoologists,
with one or two exceptions, such as Etienne Geoffroy St.-Hilaire. At
first two alternatives only were considered. _Ornithorhynchus_ was
either oviparous (egg-laying) or ovi-viviparous, that is, producing
eggs which hatch within the parent body. But with the discovery in 1824
by Meckel, the great German anatomist, of the mammary glands, a third
possibility was manifested. Did the platypus produce its young alive?
Blainville and Meckel thought so. Home, and after him the great Richard
Owen, stood out for ovi-viviparity. The St.-Hilaires in France, more
especially Etienne Geoffroy, fought determinedly for oviparity. The
controversy raged for eighty years, significant evidence being rejected
from time to time because it did not fit in with the preconceived
notions of the person to whose notice it came; and the question was not
settled until 1884, when Caldwell reported his finding of the eggs.
Yet another controversy, which can scarcely be said to have been
settled even yet, has been concerned with the spur which is found upon
the hind limb of the male. This was first described by Shaw (1799), who
includes it as a sixth digit, but mentions that it resembles a strong,
sharp spur. Home, who also described it, suggested that it was used
for holding the female in the sexual embrace. Jamison (1818) first
mentioned the serious results of wounds inflicted by it. A number of
independent observers in the early twenties--Hill, Traill, Blainville,
Knox and others--described the spur and its duct and gland with varying
degrees of completeness. Martin and Tidswell made a fairly exact
investigation of the nature of the fluid secreted by the gland, and of
its physiological effects. Numerous writers have quoted cases of severe
wounds, while others, including Dr. George Bennett, who handled large
numbers of male platypus, never knew the animal to attempt the use of
its spurs for offensive purposes.
The mammary glands differ from those of mammals in general, and may be
considered as modified sweat-glands. They open by a number of pores
upon a small area of skin, there being no teats. After the end of the
breeding-season they become so small as to be easily overlooked, and
will apparently yield no milk at the time when the young are just
hatched from the egg. In these respects they differ very markedly
from the milk glands of ordinary mammals, and have afforded ground
for further lively arguments. The fiercest opponent of their mammary
function was Etienne Geoffroy; he was prepared to take any view other
than the obvious one, which seemed fatal to his oviparity hypothesis.
The nesting habits of _Ornithorhynchus_ have also taken a long time to
elucidate. The early accounts of the nests are derived from information
supplied at secondhand, and their fantastic nature may be due to
misunderstanding on the part of the recorder. Hill (1822, p. 622)
writes:--
“... a female _Ornithorhynchus_ had been brought in alive, having
been found on its nest in a lagoon near Campbell’s River, by Mr.
Rawley, who says that he was obliged to tear the nest to pieces
before he could get the animal out, the nest being formed of reeds
and rushes, with a long tube or entrance into it, out of which the
bill of the animal only was visible.”
It is easy to imagine that what Mr. Rawley really said was that he had
to dig out the long tube, or burrow, and that, when he came to the
nesting-chamber itself, the nest was made of reeds and rushes, out of
which only the bill of the animal was visible. Maule (1832) gave the
first account of the burrow, which was more fully described by Dr.
George Bennett a little later. G. F. Bennett (1877) and Kershaw (1912)
have increased our knowledge of the nesting habits.
Although at least the natural habits of the platypus have been
ascertained, its life history and development are incompletely known.
Development in the egg prior to the laying has been dealt with by
Wilson and Hill (1908). Similar material obtained by Caldwell in 1883
was never described. A small number of ‘mammary foetus’ stages from
the burrow have been dealt with by Owen, Parker, Poulton, Wilson, and
others.
Finally, the habits of the platypus have been variously reported by
different observers, some of whom would seem to have drawn upon a
lively imagination for many of their ‘facts;’ moreover, the original
accounts have become garbled in repetition. Most of the tales might
have been disproved once for all by one or two published statements
from colonists who were familiar with the animal. Curiously enough,
however, there are no local accounts--at any rate, I have not been
able to find any--during the first half of the nineteenth century. We
owe all our early knowledge to English officials and visiting French
naturalists. While scientific Europe thirsted for enlightenment, the
colonist went blandly on with his pioneering. Fletcher (1901) has
pointed out the main reasons for the apparent neglect of zoology in the
early days of the colony. Sir Joseph Banks, who organized the early
collecting, was more interested in botany; also, that study seemed more
likely to have an economic value. So, while the flora was assiduously
collected, catalogued, and described, the fauna was practically
neglected. Nevertheless, such was the interest in _Ornithorhynchus_
that in 1840 Broderip was able to write:--
“The form is now as familiar to us as most of our European animals,
and with regard to its organization and natural history, it is
perhaps better known than many.”
Bennett (1860, p. 94) writes:--
“Of all the Australian mammalia, none has excited so much attention
as the Platypus or Water-Mole (_Ornithorhynchus paradoxus_ Blum.),
both from its peculiar form, and the great desire evinced to
ascertain the habits and economy of so singular a creature.”
Lesson’s opinion has been quoted above. Shaw (1800, p. 229) says:--“Of
all the Mammalia yet known it seems the most extraordinary in its
conformation”; and again (1809, p. 80):--
“This most extraordinary and dubious quadruped is a native
of Australasia.... If there be no mistake in the anatomical
disquisitions hitherto made on the Duckbill, its internal structure
is not less extraordinary than its external....”
Verreaux (1848, p. 128) commences his account:--
“The _Ornithorhynchus_ is an animal bizarre of structure, and offers
numerous analogies with a host of different species and even classes.
In its external form it resembles in some degree the mole as to its
body, the beaver as to its tail, and the duck as to its beak. Its
internal structure, more astonishing still, resembles that of certain
reptiles, and appears to form a link between the Mammals and Lizards.”
Every writer upon the platypus begins with an expression of wonder.
Never was there such a disconcerting animal! This wonder finds a
very curious expression in the determined efforts made to retain
Blumenbach’s name _paradoxus_, against all the rules of zoological
nomenclature. Even Everard Home, the English anatomist, writing less
than two years after the publication of Shaw’s original description,
uses the name given by the German author.
An amusing and barefaced attempt to justify the use of Blumenbach’s
name is that made by Chenu (1879). On p. 349, after mentioning that
Shaw in 1792 had described the echidna under the name of _Myrmecophaga
aculeata_, he continues:--
“... four years later, Blumenbach, in 1796, having observed a skin
of a curious animal which Banks had sent him, was struck by the
resemblance of the curious kind of beak which terminates it to that
of a duck, and made it the type of a new genus, which he called,
because of this, _Ornithorhynchus_ ...; he applied also appropriately
to the species the name _paradoxus_.... Shaw, not knowing
Blumenbach’s work, made the same animal the type of his _Platypus
anatinus_.”
Shaw could scarcely have been expected to know Blumenbach’s work,
since it did not appear until the year after his own description. In
1796, the year to which Chenu attributes Blumenbach’s observations,
the platypus had not been discovered in Australia. But Chenu has not
finished, and on p. 352 he writes:--
“As we have said in our general account of the Monotremes, the
genus _Ornithorhynchus_ was created, in 1800, by Blumenbach;
this name, most happily chosen since it recalls one of the best
characters of the included species, has nevertheless been changed
by some zoologists. _About the same time as Blumenbach_, Shaw has
named it _Platypus_, and Wiedemann, _Dermipus_; but the name of
_Ornithorhynchus_ has generally prevailed.”
Despite this brave effort to establish Blumenbach’s priority, Shaw’s
specific name is now in general scientific use, though popular works on
natural history frequently use the _paradoxus_ of Blumenbach.
Before considering the platypus in all its aspects, a few general
considerations may help to a better understanding of this ‘mystery
mammal.’ To begin with, it must be borne in mind that existing
monotremes are the survivors of a group which once formed the
aristocracy of the animal kingdom. The Tertiary is commonly referred
to as the Age of Mammals; but in late Mesozoic times there existed
mammalian forms which must have been the first wearers of hair and
drinkers of milk, and which were, in their day and according to their
manner, the lords of creation. They were mammals of a relatively
simple type and of a low grade of organization; but there was nothing
above them. In great part, however, they almost literally rose on
stepping-stones of their dead selves. The higher types to which they
gave origin easily defeated them in the competition for existence--ate
them, starved them out, thrust them into corners--and themselves went
forward to still higher destinies.
The family trees of man and the platypus probably have a common origin
in this group of primitive Mesozoic mammals. At the time, however,
there was not even the faintest foreshadowing of man--not so much
as an insignificant tree-shrew, which is supposed by many to be the
kind of stock from which he sprang. But the anatomical features which
the platypus and the echidna possess in common, and by virtue of
which they differ from all other mammals, were, it is fairly certain,
characteristic of the whole primitive group of Mesozoic mammals; in
regard to these structural features the monotremes have not evolved at
all.
Professor W. K. Parker, in his _Mammalian Descent_ (1885), writes:--
“At present, I have only partially worked out the young of one of
these kinds--the _Ornithorhynchus_; but although tolerably familiar
with the structure of the Vertebrata generally, I am at a loss, even
in this early stage of research, to see the meaning of many things in
that type.
“Here is a beast--a primary kind of beast, a _Prototherian_--whose
general structure puts it somewhere on the same level as low
reptiles, and old sorts of birds; but in which there are characters
much more archaic than anything seen in Serpents, Lizards, Tortoises,
Crocodiles, or in Emeus. Therefore the existing reptiles and birds
must stand aside as having nothing to do with the family tree of the
Monotremes, although in some things they are like these beasts, and
many of their organs are formed on a similar pattern; they are all
equally below the morphological level of the nobler Mammalia.”
Apart from its primitive simplicity, however, the platypus is a very
highly specialized animal--a statement not so self-contradictory as it
may seem at first sight. Man himself owes his dominant position to the
simplicity of his hand and the specialization of his brain. Kipling’s
jungle folk, wanting a name for the human infant which has strayed into
their midst, cannot find one among the mammals, and are forced back to
the Amphibia--to Mowgli the frog. Man has retained a simple body, which
has escaped the need for specialization because his evolution has been
projected outside himself into an evolution of tools and weapons. Other
animals in need of tools and weapons must evolve them from their own
bodily parts; we therefore frequently find a specialized adaptation to
environmental needs grafted on to primitive simplicity of structure.
Without troubling about its internal anatomy, which presents many
archaic features, let us shortly balance the primitive external
features against others which show specialization to the peculiar
environment and mode of life of _Ornithorhynchus_. The platypus is an
aquatic mammal, but its bodily form shows no very marked adaptation
to aquatic conditions. During countless ages of life in the water it
has not developed the ‘stream-lines’ of porpoises and seals. Its body
is squat, clumsy, and reptilian, as are its short, thick limbs. The
adaptations to aquatic life are mainly two: the enormous webbing of the
fore-foot or paw, which is the actual swimming-organ, and the flattened
tail, which is used as a rudder and helps in diving. Its habits in the
water can be judged accurately enough from its form. It is not a rapid
swimmer, nor an especially graceful one. It has quiet and leisurely
ways, the quick dive when alarmed constituting its one speedy movement.
The arrangement of the hair is primitive. It lies straight along
the back and belly and the upper and under surfaces of the limbs;
but falls away gradually on the sides, following the slope of the
surface. There are none of the special sensory hairs (vibrissae)
which are almost universal in mammals,--the ‘whiskers’ of the cat
will serve as an example. Against this simplicity we must set the
extraordinary specialization of the muzzle,[1] with its innumerable
special nerve-endings and its remarkable shape. It is easy and usual
to compare this muzzle to the beak of a duck. Superficially, the two
are much alike; in underlying structure, however, they are totally
unlike, and it is with the muzzle of the lower mammals that comparison
must be made. The integument is not horny, like that of a bird’s beak,
but soft, moist, flexible, and extremely sensitive. The under-water
life of the platypus is that of a blind animal. Keeping its eyes and
ears tightly shut, it feels its way by means of the touch-corpuscles
arranged all over the surface of its muzzle; by touch, combined
probably with its “sixth sense,” it also finds its food. Altogether,
the muzzle of the platypus is possibly the most remarkable organ for
sensory perception found in the Mammalia. The resemblance to the beak
of a duck has resulted from the similarity of the feeding habits of the
two animals. The common use of terms such as ‘horny’ or ‘leathery’ is
due to the fact that in stuffed specimens the soft, moist integument
dries, hardens, and becomes thinner; but this circumstance is very
misleading, as an examination of the living animal will show.
[Illustration: UPPER AND LOWER JAWS FORCED WIDE OPEN.
The normal opening does not exceed about 45 deg.
1. Nostril; 2 & 3. Secateuring ridges; 4. Serrated portion of lower
lip; 5. Free end of tongue.
(_From a fresh carcass_)
_Plate 3_]
[Illustration: JAWBONES, SHOWING DIVIDED EXTREMITIES.
From same specimen as Plate 3, after drying.
_Plate 4_]
It will be seen in Plates 3 and 4 that both the upper and lower
jawbones of _Ornithorhynchus_ are divided at their anterior ends. They
are also pliable and permit of the lips being puckered to the extent
of forming thereby a small central suction tube. It seems probable
that, by pressing the sides of the lower lip tightly against the upper
jawbones, the maximum of food-matter is sucked in with the minimum
of so-called mud. Most observers agree that the animal feeds to some
extent on minute matter, such as the eggs and larvae of aquatic fauna
found on the bed of the river. A suction system such as that described
would be by far the surest method of obtaining such delicacies, as less
sediment and foodstuffs would be disturbed by the gentle methodical
probing of closed jaws than by abrupt champing or puddling.
The small, bright eyes are remarkable only for their position high up
on the head. Since they are not used for vision under water, they have
come to be placed where they will be of most service to the animal
as it floats at the surface, munching its catch. The absence of an
external ear would seem to be a primitive character; in its place there
is a curious modification of the orifice of the auditory meatus. This
orifice lies at the posterior end of a facial furrow, the eye lying at
the anterior end, while the furrow is incompletely divided into two
by an oblique fold of skin. The edges of this furrow act as a long
pair of lids, by means of which both eye and ear may be tightly closed
at the will of the animal. The aural aperture can also be dilated and
contracted while the eyes are open, and can be “cocked” to catch sound
(see Plate 6, fig. 2). The arrangement of the lids serves also to keep
out water while the animal is submerged, and earth while it is engaged
in burrowing.
The limbs are primitive and reptilian in general form, and progression
on land is clumsy, shuffling, and sinuous, like that of a heavy-bodied
lizard. The platypus can, however, raise its body off the ground when
moving fast, though it does so only occasionally. The fore-paws serve
both as the chief organ of locomotion in the water and as the burrowing
tool. The extensive web is used only for swimming, and is folded away
under the palms during running and digging operations. Being used
for digging, the claws of the fore-paws are straighter, broader, and
stouter than those of the hind feet. Both paw and foot have preserved
the full primitive number of five digits. The feet are also very useful
and versatile. Apart from their ordinary functions, when burrowing they
can be reversed for backward progression; in self-defence they are used
to grip the foe before applying the spurs; and during copulation they
are indispensable. They are also used for toilet purposes.
The mouth exhibits a high degree of specialization. The true teeth
(which are, in any case, reduced in number to a few molars and
premolars) are lost early, and their place is taken by horny plates.
Anteriorly occur two pairs of horny ridges, which are not preceded by
teeth, and which serve to hold and kill the slippery prey; this is
then passed back and kept segregated by the large bulb which forms
the hinder part of the tongue. Two peculiar tooth-like projections,
directed forward from the anterior border of this swollen portion,
are of service in guiding the food to one side or the other as may be
necessary, and possibly for manoeuvring the grit, etc., contained in
the pouches.
My observations on the cheek-pouches of the platypus have led me to
think that what has been written about their use for storing foodstuffs
must be wrong, and in order to test my theory I secured (by concussion)
three specimens of feeding platypus immediately on their appearance at
the surface of the river. I found grit, mud, sediment, and the broken
remains (including legs, wings, and hard coverings) of small aquatic
fauna, not only cramming the pouches, but covering, in quantity, each
set of grinders also. In their entrails, however, mud was the only one
of these traceable.
Never yet have I found in the pouches sufficient remains of any one
creature to determine its specific kind. I confess myself no expert
in that branch of research; nevertheless, one would certainly expect
to find at least something recognizable if the pouching of foodstuff
beneath water was usual. Because of their bulk, adult shrimps and
other large-sized prey cannot possibly be pouched whole, nor can
they be passed through to the grinders before being dissected by the
secateuring ridges of the bill; this I have frequently observed while
feeding platypus in captivity. The necessary act of dissection, prior
to mastication, takes place while the animal is floating with its bill
skimming the water; therefore large prey must be carried up to the
surface in the bill-like section of the capacious jaws.
These observations suggest to me that the purpose of the cheek-pouches
is to act as containers of grit rather than as receptacles for food.
The pouches open out at each side directly on to the grinders, which
project very little above the level of the jaws, and my opinion is that
the coarse grit aids considerably in their functioning as teeth, and,
further, tends to toughen the gums and thus convert them into grinders,
maintaining these essential conditions after the true teeth of the
nestling stage have disappeared.
The fact that only the hard remains of foodstuff are found mixed with
the grit may mean that this mixture is drawn upon and repouched,
as occasion demands, over and over again; but whether the grit is
deliberately pouched before meals, or collected haphazard, or even
accidentally, with the food, I cannot say. It probably depends on the
class of food offering at any particular time and on the frequently
changing conditions of river beds--from mud to sand and shingle or
otherwise--according to varying seasonal changes by which platypus and
its many forms of living prey are naturally ruled.
It should be understood that the platypus, from choice or necessity,
consumes various kinds of food, that some kinds are normally available
only at certain times of the year, and that in abnormal seasons the
variety, as well as the quantity, would be affected. At such times
one finds platypus gorging themselves with inferior muddy matter,
which would not, by preference, be included in their bill of fare. The
various statements made on this subject by observers may, therefore,
all be correct, though each is sceptical of the accuracy of the others.
Finally, mention must be made of the curious integumentary flap which
projects backwards from the base of the naked muzzle, both above and
below. This is not altogether, as has sometimes been suggested, a
shield for the protection of the head during feeding and burrowing.
It is an extension of the area for sensory perception, and from its
position would appear to serve much the same function as the “whiskers”
about the mouths of other mammals.
To this mixture of old and new physical characteristics there must
correspond a somewhat similar mixture of psychological characteristics.
Much of the behaviour of the platypus cannot be adequately explained
by its present conditions of life, and there is no obvious reason why
it adopted its present extraordinary precautions for the safety both
of itself and of its young. The Murray cod and the monitor lizards may
have eaten the platypus out of certain rivers, since there seems to
be nothing that they will not eat; but of this there is no reliable
evidence. The instinct for caution must be a heritage from some olden
time, when it had to contend with conditions much more strenuous.
During that period, which our imagination cannot reconstruct, the
ancestral platypus may have used its cerebral cortex to the full for
the winning of a livelihood in open competition, and for keeping
safe, not only itself, but its young. It has a large brain for its
size, proportionately much larger than those of many of the lower
Didelphia and Monodelphia. Its brain does not show any of the furrowed
convolutions which are looked upon as indicating a high degree of
mental development, but the smooth condition may have been acquired.
The brain of echidna, which is in general a much more stupid creature,
is convoluted, and indicates that this animal still has enough worries
to produce wrinkles on its cortical surface.
[Illustration: SKELETON OF PLATYPUS.
Sketched from specimen in the Australian Museum, Sydney.]