GENERAL CHARACTERISTICS
The general form of the platypus is by now familiar to all. It appears
stuffed and mounted in all natural history museums, and illustrations
of it adorn all ordinary natural history books. Yet, strange as it may
seem, I have never seen a correctly mounted specimen in a museum, nor a
correct figure of the whole animal in a book.
The most conspicuous feature about the bodily form of the platypus is
its prevailing flatness. The naked muzzle is broad and flat; the head
is so much depressed that the eyes have become more dorsal than lateral
in position; the trunk is broad and flat, though in profile its outline
rises from the shoulders to a point a little behind the middle of its
length, and then falls towards the tail; a cross-section has the form
of a low arch, a good deal more broad than high; finally, the tail is
broad and flat, with a broadly rounded tip.
The skin, kimono-like, is over-large for the size of the body, and,
except at all the animal’s extremities, it appears to be entirely
dissociated from the primary nervous system. That is to say, a platypus
will readily respond to the slightest touch on either feet, paws, bill,
lips, or tail, but will not shrink from being soothingly stroked, from
forehead to rump, along the fur. This characteristic is most apparent
while the animal is submerged in water, where it is unable to see,
hear, or smell the experimentalist.
[Illustration: (1) HEAD OF FEMALE PLATYPUS, SHOWING DIRECT DORSAL
VISION.
In this instance the eyes, which are situated above the white patches,
are closed.
_Plate 8_]
[Illustration: (2) VENTRAL VIEW OF LIPS.
Note how sides of lower lip are pressed tightly against upper jaws,
leaving space in centre for sucking in foodstuff.
_Plate 8_]
The muzzle with its backward-projecting flaps is naked, as also are
the upper surfaces of the digits of paws and feet, and the palms and
soles. All the rest of the body is covered with hair, which is of
two main kinds. Closely investing all the body except the tail
and extremities of the limbs is a fine dense under-fur, beyond which
project the ends of a much longer and harsher kind of hair, with highly
polished tips. The under-fur is woolly, grey at the base, inclining to
brownish at the outer ends. The longer hairs are remarkable in that
their projecting portions are flattened, giving them a lance-like
appearance, and are generally curved so that the ends turn in to the
fur. On the animal’s back and sides these hairs are usually dark
brown in colour, but the tips are frequently silvery white, or, in
reddish individuals, golden yellow. The prevailing paler colour of
the under surface is due to the absence of dark pigment from the ends
of these hairs, which have grey basal portions and tips ranging from
silver-white through yellow to chestnut and (in some cases) deep
ferruginous brown.
This longer fur determines the animal’s colour, which is variable
within fairly narrow limits. The usual coloration is deep umber-brown
on the back and sides of head and body and upon the exposed surfaces of
the limbs; but reddish individuals are not uncommon, and some examples
are almost black. The ends of the long hairs are frequently curly, and
the prevailing ground-colour becomes powdered, as it were, with silver
or gold, in consequence of the different colour of the tips.
The hair on the dorsal surface of the tail is coarse, and without
flattened tips. Owing to the constant dragging of the under-side over
the ground, this surface is usually denuded of hair, but in young
individuals a delicate silky fur is present, usually of a golden
colour, but ranging to warm brown.
The ventral surface of the body is described by Thomas (1888, p. 389)
as ‘dirty greyish white’, which hardly does justice to the beauty
of the fur on this part. It ranges from silver through yellow to
warm chestnut, being lightest on the chest and throat, and darkening
posteriorly. Old males sometimes have the whole ventral surface a warm
brown in colour, with darker markings about the chin, limbs, and vent.
The colour is, in all instances, due to the highly polished tips of
the longer hairs, which have a brilliant sheen comparable with that
of the breast-feathers of the tippet grebe (see Plate 7). An albino
is recorded by Bennett, and one is exhibited in the Mammal Gallery of
the Australian Museum, Sydney. Sometimes, too, the black skin of the
extremities is mottled with white.
The coat of the platypus is devoid of stripes, bars, spots, or
pattern of any description, save for a small yellowish-white to
yellowish-brown spot placed just beneath the eye. Bennett (1860, p.
98) correctly described this spot, and noted that it occurred, with
a single exception, in all specimens of either sex which had come
under his observation. Thomas (1888, p. 389) dismisses it briefly
as ‘a spot round each eye white or yellowish.’ Wood Jones (1923, p.
46) remarks--“There is said to be a ‘white or yellowish’ area around
each eye; but this area, though almost always emphasized in text-book
accounts of the animal, is not invariably present.”
To describe this spot as ‘around the eye’ is misleading. In some
individuals the very slightly differentiated upper eyelashes certainly
are light in colour, but it is only to this extent that the spot may be
said to surround the eye. It is, as Bennett describes it, immediately
below the inner angle. It is, moreover, present in all the platypus
I have seen, including specimens from Queensland and Tasmania in the
Australian Museum collections. That it is not invariably present is
indicated by Bennett’s observation of an individual without it. Home
(1802, p. 70) also records its absence in a male which he examined;
he judged from its presence in the female that it was a character for
the distinction of the sexes. This is not so, since it is commonly
present in males. In dried skins, if the head be not fully filled out,
it sometimes becomes involved in the facial furrow, and thus escapes
notice; in spirit specimens, as well as in those wet with water, it is
often curiously inconspicuous. Thus, out of ten photographs of the one
animal illustrating the articles of Hornaday and Joseph (1922) which
show the eye, only two (on pages 108 and 109) show the spot clearly. In
one or two of the others it can just be made out, but in most it is not
visible. Yet it is ordinarily a conspicuous mark, whether on dry land
or under water, as may be judged from both subjects shown on Plate 6.
The hair of the platypus, as has been mentioned in the first chapter,
has a general fore-and-aft direction, and, apart from the different
kinds of hair described above, the only differentiation is to be found
in the region of the facial furrow. Here the hair surrounding the eye
is slightly modified to form eyelashes of a rudimentary nature, and the
aural orifice is lined with short fine hairs, which help to prevent
water and particles of soil from gaining admittance. There are no
specialized sensory hairs in any part.
The muzzle, which shows some resemblance to a duck’s bill in the dry
condition, is very different in the living animal. The naked skin is
thick, but soft, moist, and flexible, very unlike the horny beak of
a bird. On the upper surface it is slate-coloured; on the under, of
a yellowish flesh-colour, often broadly mottled with greenish slate.
From the base of each mandible a cuticular flap projects backwards
over the fur of forehead and throat. The dorsal flap is longest in the
middle line of the head, varying from 17 to 20 mm. in length, and is
shorter at each side. The ventral flap is wider at its base than the
dorsal, and has a shallow emargination in the middle of its posterior
border. Although described separately as dorsal and ventral flaps,
these really form round the base of the muzzle one continuous collar,
which is only partially divided into dorsal and ventral portions by
deep dorso-lateral emarginations. The nostrils open upon the upper
mandible at about a third of its length from the anterior end. They are
oval apertures with a slight rim-like border, set close together at
each side of the middle line. Their anterior borders lie very close to
each other, but they diverge obliquely behind. The dorsal portion of
the muzzle measures, in an individual of average size, 60 mm. long by
50 mm. wide; it considerably overlaps the ventral portion, which in the
same individual measures 42 mm. by 38 mm. (see Plate 8).
The muzzle, with its flaps, is a highly specialized sense-organ. The
whole of its exposed surface, both above and below, is pitted with
minute pores, which extend on to the cuticular flaps and mark the sites
of the highly specialized touch-corpuscles. When under water, the
animal depends principally on its delicate sense of touch for finding
its way about, and it is fairly certain that the same condition obtains
in the burrow. Even when in the open air, it probably depends largely
upon the muzzle, since its eyes are so placed that it cannot easily see
objects straight in front of it on the ground. The anterior border of
the upper mandible is, from its position, the part most brought into
use for testing objects, and would seem to be especially sensitive,
for the platypus strongly resents its being touched, notwithstanding
that it is used for shovelling away loose earth and for upturning
river shingle. But the general distribution of touch-corpuscles over
the whole of the naked area indicates that all parts are sensitive;
and their continuation on to the flaps carries a sure implication that
these, too, subserve a sensory function. Many dangers threaten an
animal nosing about blindly under water; and it seems probable that
the extension of the tactile area in this way is a provision against
entering crevices and crannies in which it might be caught. It is
well known that it can squeeze through very narrow spaces, and it is
possible that the flaps are used as a gauge by means of which it can
tell whether it is safe to go on, or wiser to withdraw. Whether this be
so or not, the flaps are assuredly a part of the great tactile organ,
and not a mechanical shield. In some of the earlier figures, drawn from
dried skins, these flaps are shown standing up at right angles from the
surface of the head; in the living animal they are always laid back
upon the fur, nor does it seem able to raise and depress them to any
appreciable extent.
[Illustration: PLATYPUS PAWS, EXPANDED FOR SWIMMING, AND CONTRACTED FOR
WALKING AND BURROWING.
Note impressions in membrane caused by coming into contact with claw
tips.
(_From fresh carcass_)
_Plate 9_]
The eye and ear are peculiarly arranged. In the half-grown young,
running across the front of the head, just under the border of the
dorsal flap, there is a groove which on each side turns backwards over
the area occupied by the eye and ear (see Plate 12). In the adult
the transverse portion of this groove has disappeared, but the lateral
portions remain as the facial furrows, in which the eye and ear are
situated. The eye, which has suffered most at the hands of artists
and taxidermists, is placed at the anterior end of the groove, very
close to the dorsal flap, by which it would be partly hidden were
not the flap emarginated a little at each side. It is rather small,
but exceedingly bright and beady, and has a dark brown iris almost
indistinguishable from the pupil. Because of its position it can see
only upwards and outwards, and its sole function would appear to be
that of detecting moving objects when the beast is at the surface of
the water or on the bank. In illustrations the eye is usually placed
in the middle portion of the furrow, that is to say, between its true
position and that of the ear. Even Gould’s plate exhibits this error.
Moreover, the eye is generally depicted too large, and often with a
light iris. The plates of Peron and Lesuer (1807) and of Lesson (1839)
show a yellow iris, and Waterhouse (1846) in his black-and-white figure
shows the iris white. A light iris has been given to many of the
specimens mounted in museums, and in these, too, the eye is usually
wrongly placed. In life the upper and lower eyelids are not well marked
off from the borders of the furrow, but may be distinguished by a
slight differentiation of the hair on their margins to form eyelashes.
There is a nictitating membrane capable of covering the whole cornea,
but I have never seen this employed by the living animal.
The portion of the furrow which contains the eye is partially separated
from the auricular part by a fold of skin running obliquely upwards and
backwards from the lower border. There is no auricle (external ear).
The aural opening is in the form of a deep pit, occupying most of the
posterior half of the furrow. The margin is lined inside with short,
soft hairs, which prevent the entry of foreign bodies. The opening
can be dilated and contracted at the will of the animal, and is in a
constant state of motion when it is alarmed or excited. Under water,
or while burrowing, the whole furrow is closed by the apposition of
its upper and lower margins, and remains so until the head once more
emerges. The dorsal position of the eyes, in conjunction with the
bulging of the cheeks (due partly to the grit in the pouches) give the
sides of the head a heavy-jowled appearance.
The head is joined to the trunk by means of a short and not very
well-defined neck. The shape of the trunk varies according to the
degree to which the animal is extended. When it is fully stretched in
walking, the body appears oblong, and twice as long as it is wide. When
squatting, the trunk appears both broader and higher in the posterior
region.
The limbs are approximately equal in length, and are highly
specialized. The metacarpal region of the fore-paw is covered with
hair dorsally; the digits are naked, and are united by a black web,
which is extended beyond the tips of the claws for a distance of
15 mm. (in spirit specimens), the extension being supported upon
leathery thickenings which take origin from the under surface of the
ungual phalanges. Each of the three middle digits has two of these
thickenings, arranged symmetrically, but the two outer digits have only
one each, placed towards the lateral margin of the paws. The claws are
short, straight, and compressed. The palm is black and naked, finely
wrinkled, but without any pads such as usually occur on mammalian feet.
The fore-paw is the chief swimming-organ, its web being capable of
considerable extension in the living creature. On land, that portion
which extends beyond the finger-tips is folded under the palm, so that
the stout claws may be used for walking and burrowing. The adaptation
to two such totally diverse functions is very extraordinary. According
to Wood Jones (1923, p. 48) the digital formula is 4 3 2 5 1; but
the three middle digits are practically equal in length. In mounted
specimens, and in illustrations, the web is always shown in the
extended condition, but the animal when on land always has the web
tucked under its palms. It is, moreover, never flat, as usually shown,
but is always arched, with a dorsal convexity, even when extended.
A somewhat remarkable transformation of the fore-claws is essential
before a young platypus can fend for itself. In the nestling stage, the
slender claws curve downwards and are grooved beneath. The reason for
this curvature is, apparently, to give the nestlings a firm grip of
the mother’s abdominal fur when vigorously nuzzling to induce a free
flow of milk (see Plate 10). As the nestling grows, the claws gradually
become straighter and broader, and instead of remaining grooved, the
nails become slightly convex below. By this time the paw is adequately
webbed for swimming, and consequently the young one is free to forage
alone (see Plate 9).
With each vigorous sweep of the paw when swimming, there is necessarily
a severe pressure of the claws against the delicate webbing, and if
the claws were not broad and regularly rounded off beneath they would
undoubtedly puncture the swimming membrane. The same thing might
happen during the toilet process. On examining living adult specimens
I have found that, not only is the under surface of the claws convex,
but the tips are slightly tilted and there is a considerable amount
of resiliency in the nails. Yet, notwithstanding all this, distinct
impressions of the tips may be clearly seen in the webbing (see Plate
9). It will thus be seen that although the platypus is a burrowing
mammal, the nails are not designed entirely for that particular
purpose. This supports my opinion that burrowing is normally attempted
only in soil where the sensitivity-lipped bill can also be used.
The hind foot is less remarkable. On the upper side it is covered with
hair almost to the ends of the digits, which are webbed. The webbing
does not extend beyond the bases of the claws, except for a peculiar
narrow prolongation on the inner margin, which lies just within the
first digit, and looks like the shadow of its claw. The claws are
laterally compressed, and strongly curved outwards and backwards. The
digital formula, according to Wood Jones, is 4 5 3 2 1. This foot is
scarcely used at all in swimming, except to help tread water, and to
aid the tail in steering. On land, the main thrust is due to the
feet, but the paws pull with a fair degree of strength. The sole, like
the palm, is black, wrinkled, and naked, except for a fringe of hair
along its inner border (see Plate 11). In the male a horn-coloured
spur is set upon the heel, with a fleshy collar about its base; this
spur is movable, and is directed backwards and inwards. In Bennett’s
figure (1860, Pl. III), as well as in a number of others contained in
authoritative zoological works, the spur is shown on the outside of
the foot. This may have been due to a laudable desire to get the spur
in at all costs, but it is apt to disconcert the seeker after precise
knowledge. In the female, a depressed socket lined with wrinkled skin
occupies a position corresponding to that of the spur in the male. The
spur is developed in the young of both sexes; in the male it grows
normally, but in the female it gradually disappears.
The tail is broad and flat, with the under surface usually a little
concave. It is about a third longer than it is wide, with sides
slightly converging as it passes backwards, and with broadly rounded
end. The hair of its upper surface is exceedingly coarse and harsh;
that of the under surface, when not entirely worn off, is softer
and lighter in colour. It is a powerful and muscular organ, and an
efficient aid in diving, as well as a somewhat less efficient rudder.
In nursing females the hair is usually found to be worn off the upper
surface. This is caused principally by pushing the pugs back into
position in the burrow. Against this view, Wood Jones (1923, p. 48)
writes:--
“On general lines, the form of the tail resembles that seen in the
Beaver; and this form is, in both animals, an adaptation to surface
swimming and rapid diving. It has nothing whatever to do (either in
the Platypus or the Beaver) with any supposed habit of puddling clay
or flattening down the floor of its burrow or nesting-chamber. When
Beavers are alarmed they suddenly smack the water with their flat
tails and dive beneath the surface. The loud sound made by the smack
of the diving Beaver acts as a warning note to other Beavers in the
neighbourhood, and it is probable that the same warning note is
produced by the Platypus. The animal has several times been described
as making a sound as it dives.”
[Illustration: (1) FEMALE PLATYPUS SUCKLING YOUNG.
Note young one clinging to fur and supported by the mother’s tail.
_Plate 10_]
[Illustration: (2) FEMALE PLATYPUS.
Note extreme looseness of skin, and tail worn bare with pugging.
_Plate 10_]
Without supporting evidence, the categorical statement that the tail
of the platypus has nothing whatever to do with any supposed habit
of puddling clay is not convincing, and I prefer to rely on my own
field observations. I must disagree also as to the warning signals.
These are common enough among gregarious animals, and the beaver is a
gregarious animal. The platypus is not gregarious, but almost solitary,
and therefore has no one to warn. Wood Jones writes, it is true, of
‘a considerable colony,’ but I have had no experience of colonies
of platypus. The rare occasions when I have found two in company
have always caused me surprise. I see no justification, therefore,
for arguing by analogy from the herd habits of the beaver to the
semi-solitary behaviour of the platypus. When surprised, and beating a
hasty retreat, the animal certainly makes a noise in diving; but this
has no significance, as I shall explain later on.
The only sure external mark of distinction between the sexes is the
spur. Full-grown males are considerably larger than full-grown females;
but the immature or young male may be smaller than the female. Ten
males taken by me during the spring over a period of several years
measured (mm.):--600, 529, 535, 538, 481, 533, 485, 475, 540, 510,
averaging 522 mm. Nine females measured (mm.):--406, 402, 414, 460,
475, 433, 451, 421, 407, averaging 430 mm.
Measurements of spirit specimens and skins in the Australian Museum
are:--
MALE. FEMALE.
Spirit Specimens. 445 mm. 398 mm.
405 mm. 392 mm.
455 mm. --
Skins 561 mm. 483 mm.
560 mm. 478 mm.
510 mm. --
537 mm. --
Average of 7 = 496 mm. Average of 4 = 413 mm.
Bennett (1860, p. 102) gives the average measurements of freshly-killed
males as from 19 to 20 inches (483 mm. to 508 mm.); and of females as
from 18 to 19 inches (457 mm. to 483 mm.).
We may next consider the nature and heat of the blood. In amphibia,
reptiles, and birds, the red blood-corpuscles are oval, nucleated
discs. In mammals they are non-nucleated, and in all save the camels
are circular. The platypus has typical mammalian corpuscles, of about
the same size as those of man. Cold-blooded animals (amphibia and
reptiles) have no heat-regulating apparatus, and their temperature
tends to rise and fall in accordance with that of the surrounding
medium, whether it be earth, air, or water. In mammals and birds,
on the other hand, the heat-regulating mechanism tends to keep the
temperature constant within a degree or two, regardless of the external
medium. This difference in blood-heat causes striking differences
in habit. The cold-blooded animal is forced to hibernate during the
winter, at least in places where there is a considerable difference
between the mean winter and summer temperatures; the depression of
temperature renders it inactive. The warm-blooded animal, on the other
hand, eats more food, and moves about actively in order to produce the
heat necessary to keep up its body temperature.
It has been claimed that the monotremes exhibit an intermediate
condition, and are not completely warm-blooded. On this point, however,
I am in full agreement with Wood Jones (1923, pp. 38-39), and quote his
discussion of the matter:--
“In the same way we must admit that the body temperature of the
Monotreme is unusually low; but that is not to agree that they are
akin to the Reptiles in failing to maintain their body temperatures
within certain fairly definite limits.
“The temperatures of seven females of the Platypus were taken by Mr.
Burrell. These females were removed from their nesting chambers, and
the observations were made in September. The temperature of these
animals ranged between 30°C. and 33°C., and the average of all the
observations was 32.2°C.
“Of _Echidna_ there are many temperature records, since it
is an animal which is easily kept and examined in captivity.
Miklouho-Maklay, in 1879, examined a series of ‘porcupines,’ and
concluded that their temperature ranged between such low figures as
from 26.95°C. and 28.3°C. In 1886, R. von Lendenfeld, as the result
of a series of observations, concluded that the body temperature
was higher, but more variable, and they give the extremes as 28°C.
and 35°C. Semon, in 1894, gave 26.5°C. to 34°C. as the range for
_Echidna_. Sutherland, in 1897, found it to be as wide as from 22°C.
to 36°C. Dr. C. J. Martin re-investigated the question in 1902,
and during the last few years Dr. Wardlaw has made innumerable
observations, and, thanks to his work, we may say that the
peculiarities of the body temperature of the Monotremes are now well
known.
“The temperature of the higher Mammals varies within fairly wide
limits, and in the different species that have been examined it
ranges from about 36°C. upwards for a few degrees. It is therefore
obvious that both _Ornithorhynchus_, with its average of 32.2°C., and
_Echidna_, with its average of 31.1°C., are creatures of relatively
low temperature; but the difference between the Monotreme temperature
and that of other Mammals is not nearly so great as it is often
asserted to be. It must also be remembered that our knowledge of
the temperatures of some of the lower Monodelphia is scanty, and it
is possible that _Echidna_ and _Ornithorhynchus_ do not stand very
far apart from some of the more sluggish and least advanced of the
higher Mammals in the matter of their bodily heat. Again, the fact
that the temperature of the Monotremes varies at different times of
the day does not confer on them the distinction that some writers
have imagined. Dr. Wardlaw determined that the morning temperature
was always lower than the afternoon temperature; but the same is true
of the higher Mammals and of man. Semon noted this variation in the
temperature, but confessed that ‘a relation between these changes
and the changing temperature of the outer air could, however, not
be proved.’ That is to say, although the temperature of _Echidna_
is variable, its rise and fall does not correspond with the rise
and fall of the temperature of its surroundings, as is the case
with the lower Vertebrates. There is, nevertheless, a time when the
temperature of _Echidna_ does tend to follow the temperature of the
outside air, and when the Monotreme can be said to behave somewhat
like a ‘cold-blooded’ or poikilothermic animal. This is during that
period of the year when the animal undergoes a partial hibernation
or aestivation. In the summer Dr. Wardlaw’s animals averaged 30°C.
in the morning and 32.6°C. in the afternoon; but in the winter the
morning temperature was 29.7°C. and the afternoon was 32.3°C.; but
this fall in winter temperature is found in all hibernating or
partially hibernating animals; and it can only be said that the
Monotremes are animals having a rather low body temperature, but,
nevertheless, being truly homoeothermic (or ‘warm-blooded’) within
certain limits of temperature, and in the non-hibernating period.
They have a typically good mammalian heat-regulating mechanism,
effective between 27.6°C. and 32.6°C.; and it is only when the
temperature is raised or lowered beyond these limits that the
regulation tends to break down, and they behave as poikilothermic
animals.”
[Illustration: (1) TOP OF LEFT HIND FOOT, WITH SWIMMING MEMBRANE FULLY
EXTENDED.
Note tip of spur projecting behind and above ankle.
(_From fresh carcass_)
_Plate 11_]
[Illustration: (2) SOLE OF RIGHT HIND FOOT.
Note base of spur unsheathed; this readily occurs after death, but
seldom during life. Compare with Plate 15 (1).
(_From fresh carcass_)
_Plate 11_]
Following is a table of cloacal and atmospheric temperatures (Fahr.)
observed by me during five years of field work.
MALE PLATYPUS.
Cloacal Atmospheric
temp. shade temp.
8/10/23 84° 53°
18/9/25 82° 63°
19/9/25 87° 79°
FEMALE PLATYPUS.
20/9/20 88° 70°
23/9/21 87° 82°
5/10/21 88° 68°
8/10/23 84° 53°
15/9/24 84° --
7/10/24 82° --
8/10/24 90° 46°
14/3/25* 90° --
24/8/25 86° 64°
24/8/25 92° 64°
28/8/25 94° --
3/9/25 82° 70°
10/9/25 89° 74°
18/9/25 82° 63°
26/9/25 86° 66°
March may be reckoned as midway between rutting periods.
* With this exception, all the females were brooders taken from nests.
Two temperature readings of wild echidna specimens, made directly after
collection in mid-September 1924 and 1925, were found by me to be
respectively:--
1. Cloaca, 90° Fahr. Pouch, containing young, 84° Fahr.
2. Cloaca, 79° Fahr. Pouch, containing young, 82° Fahr.
I did not record the atmospheric temperature when the 1924 specimen
was taken; but I noted that it was an exceptionally cold day. When the
second was taken, it was 70°.
By attaching an adult platypus to a spring scale I found that it
could pull steadily (on level ground) six pounds, and up to twelve
by jerking. The bottom jaw, when open, can pull seven pounds in the
gradual closing.
Characteristics common to the platypus, to reptiles, and to birds are
the single aperture or vent into which the intestinal, urinary, and
reproductive systems open, and the laying of eggs. The “scientific”
name (_Ornithorhynchus_) together with its commonly-accepted early
vernacular name of “duckbill,” its webbed feet, and the discovery of
its eggs have contributed to the existing impression, except among
zoologists, that the platypus is essentially bird-like; but, as a
matter of fact, while it is clearly a mammal, its remote origin has
been proved to be reptilian. Apart from this scientific conclusion I
would like to outline for general readers some external characteristics
of the platypus which I consider to be possessed also by certain
reptiles.
The study of an animal in its adult stage is apt to lead one to look
for its relations in more modern forms, whereas in its embryo and
nestling stage it is more likely to exhibit the characteristics of
its forbears. By looking backward we may, therefore, occasionally
detect a trait connecting the platypus with much earlier forms in the
evolutionary cycle--a trait which in the mature animal would easily
escape notice, even if it had not entirely disappeared.
To begin with the egg--quite apart from the leathery texture of the
capsule, the fact that the foetus has developed to a considerable
extent before deposition is positively reptilian in character.
The tortoise-like overturning of a platypus, though inconspicuous
in the adult, is, nevertheless, deliberately and systematically
accomplished by the unfurred nestling, and this at a stage when their
limbs are of little assistance. Like a tortoise, a young platypus,
when floundering on its back, pivots its snout firmly in the ground,
then arches its neck, throat uppermost, until, by such strenuous
leverage, the shoulders are sufficiently raised to allow the wriggler
to over-balance on to its abdomen.
Another reptilian trait peculiar to the young of platypus is their
power of endurance when wholly submerged in water, and, strange though
it may appear, the younger the subject the greater that power. This is
described more fully in the chapter on the breeding-burrow.
The male platypus and echidna are the only known mammals with poison
glands, and this forms another link with the reptiles.
From a dorsal aspect, the fur-tracts of _Ornithorhynchus_ trend
uniformly towards the tail, in a manner similar to that of the scale
pattern conspicuous in snakes, etc. It is true that slight semi-whorls
or waves of fur occur ventrally, and about the cheek-pouches, but even
this is not entirely wanting in the scale pattern of reptiles.
Spurs, or “hooks” as I prefer to call them here, are to be found on the
fore-flippers of the male Green Turtle; but whether they are used as
weapons of defence I cannot say. My opinion is that, like those of a
platypus, defence is one of their purposes. From personal observation
of both creatures, however, I know that their hooks are used for
gripping during copulation. Incidentally it may be remarked that both
of these creatures perform this function in water. It is of prolonged
duration in both cases; therefore an untiring grip is essential.
The casual gait of a platypus is somewhat akin to that of a
Stump-tailed Lizard, while the chubby tails which both animals possess
are sufficiently near in design not to be overlooked in this matter.
The small and beady bright eyes of _Ornithorhynchus_, also their
position and the direction of their vision, are similar to those of
certain reptiles, as is also the dorsal position of the rigid nostrils.
Although represented in swimming birds, the webbing of the feet of the
platypus is found also in reptilian quadrupeds.
The contorting ability of an adult platypus is quite remarkable. It
can extend its length six inches without raising its abdomen from the
ground. When it is in a crouching attitude, with the back conspicuously
humped, it is impossible to see daylight below, and the contour of
the whole body resembles that of a squatting echidna. When lying
fully extended on its back, the platypus can, by placing the lower
portion of its bill on its breast, and without raising its head to
any appreciable extent, double itself ventrally until its head passes
its tail, and that pliable member is itself doubled until the creature
becomes normally righted on all fours, dragging its tail behind it.
This act it can accomplish in a tunnel equal in circumference to the
performer so doubled. When balled-up, as in the sleeping position,
the tip of its tail will reach over the head to the scapular region.
In the reversed position the tail-tip reaches to the gullet, above
the back. In turning sideways, with abdomen on the ground the while,
tail and bill just make contact. The head can be turned sideways at a
right angle to the body, and the tail can be moved either to form a
right angle with the rump or to lie comfortably along the contour of
the back, except at the base, where one can just insert the tip of an
index finger. These few items are additional to the animal’s capacity
for muscular expansion and oscillating limb-functions, and they give
some notion of what the platypus is capable of when hard pressed or in
a tight corner.
Finally, the platypus, like the reptiles, has no external ears and is
flealess, though ticks are common to both. One is known by the company
one keeps.
[Illustration: (1) HEAD OF INFURIATED MALE PLATYPUS.
Note serrated edge of bottom lip.
_Plate 12_]
[Illustration: (2) NESTLING PLATYPUS, ABOUT FIVE WEEKS OLD.
Note swimming membrane extending beyond claw tips of fore-paw; grip
of hind foot and tick on thigh; also that the eye is closed and the
ear-hole open.
_Plate 12_]