CHAPTER I. Introductory

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, 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.

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]

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.

Sketched from specimen in the Australian Museum, Sydney.]