Online Encyclopedia

PLATYPUS

Online Encyclopedia
Originally appearing in Volume V21, Page 828 of the 1911 Encyclopedia Britannica.
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PLATYPUS. The duck-billed platypus (Platypus anatinus) was the name assigned to one of the most remarkable of known animals by George Shaw (1751-1813), who had the good fortune to introduce it to the notice of the scientific world in the Naturalist's Miscellany (vol. x., 1799). In the following year it was independently described by Blumenbach (Voigts Magazin, ii. 205) under the name of Ornithorhynchus paradoxus. Shaw's generic name, although having priority to that of Blumenbach, could not be retained, as it had been used at a still earlier time (1793) by Herbst for a genus of Coleoptera. Ornithorhynchus (Gr. Opts, opvtOos, bird, and biyXos, bill) is therefore now universally adopted as the scientific designation, although duck-billed platypus (Gr. arAarir, flat, and robs, foot) may be conveniently retained as a vernacular appellation. By the colonists it is called " water-mole," but its affinities with the true moles are of the slightest and most superficial description. The anatomical differences by which the platypus, and its only allies the echidnas, are separated from all other mammals, so as to form a distinct sub-class, are described in the article MONOTREMATA, where also will be found the main distinctive characters of the two existing representatives of the group. It is there stated that the early stages of the development of the young are not yet fully known. Sir R. Owen, and later E. B. Poulton, showed that the ovum of the platypus was large compared with that of other mammals, whilst W. H. Caldwell showed that it was filled with yolk, and finally established the fact that Platypus as well as Echidna is oviparous. Two eggs are produced at a time, each measuring about three-fourths of an inch in its long and half an inch in its short axis, and enclosed in a strong, flexible, white shell. The 'platypus is pretty generally distributed in situations suitable to its aquatic habits throughout the island of Tasmania and the southern and eastern portions of Australia. V Ep (After F. E. Schultze, %gl. Preuss. Akad. der Wissenschaft, Berlin, r8gs.) A, a small specimen drawn from life. The spherical granules (G) are probably gland-secretions; the dark bodies (Z) are probably xanthellae, i.e. algal cells living in association with the animal. B, a specimen undergoingfission. C, part of a vertical section. D.Ep, The dorsal epidermis. V.Ep, Ventral epidermis. The G, Refringent corpuscles. hair-like processes are PC, Parenchymatous cells. cilia. The length of the animal when full grown is from 18 to 20 in. from the extremity of the beak to the end of the tail, the male being slightly larger than the female. The fur is short, dense and rather soft to the touch, and composed of an extremely fine and close under-fur, and of longer hairs which project beyond this, each of which is very slender at the base, and expanded, flattened and glossy towards the free end. The general colour is deep brown, but paler on the under parts. The tail is short, broad and depressed, and covered with coarse hairs, which in old animals generally become worn off from the under (From Gould's Mammals of Australia.) Platypus. surface. There are no true teeth in the adult, although the young possess a set which are shed after being worn down by friction with food and sand, their purposes being afterward served by horny prominences, two on each side of each. jaw—those in the front narrow, longitudinal, sharp-edged ridges, and those behind broad, flattened and molariform. The upper surface of the lateral edges of the mandible has also a number of parallel fine transverse ridges, like those on the bill of a duck. In the cheeks are tolerably capacious pouches, which appear to be used as receptacles for food. The limbs are strong and short, each with five well-developed toes provided with strong claws. In the fore feet the web not only fills the interspaces between the toes, but extends consider-ably beyond the ends of the long, broad and somewhat flattened nails, giving great expanse to the foot when used for swimming, though capable of being folded back on the palm when the animal is burrowing or walking on the land. On the hind foot the nails are long, curved and pointed, and the web extends only to their base. On the heel of the male is a strong, curved sharply pointed, movable horny spur, directed upwards and backwards, attached by its expanded base to the accessory bone of the tarsus. This spur, which attains the length of nearly an inch, is traversed by a minute canal, terminating in a fine longitudinal slit near the point, and connected at its base with the duct of a large gland situated at the back part of the thigh. The whole apparatus is so exactly analogous in structure to the poison-gland and tooth of a venomous snake as to suggest a similar function, and there is now evidence that it employs this organ as an offensive weapon. The platypus is aquatic in its habits, passing most of its time in the water or close to the margin of lakes and streams, swimming and diving with the greatest ease, and forming for the purpose of sleeping and breeding deep burrows in the banks, which generally have two orifices, one just above the water level, concealed among long grass and leaves, and the other below the surface. The passage at first runs obliquely upwards in the bank, sometimes to a distance of as much as so ft., andexpands at its termination into a cavity, the floor of which is lined with dried grass and leaves, and in which, it is said, the eggs are laid' and the young brought up. Their food consists of aquatic insects, small crustaceans and worms, which are caught under water, the sand and small stones at the bottom being turned over with their bills to find them. They appear at first to deposit what they have thus collected in their cheek pouches, and when these are filled they rise to the surface and quietly triturate their meal with the horny teeth before swallowing it. Swimming is effected chiefly by the action of the broad forepaws, the hind feet and tail taking little share in locomotion in the water. When asleep they roll themselves into a ball, as shown in the figure. In their native haunts they are extremely timid and wary, and very difficult to approach, being rarely seen out of their burrows in the daytime. Mr A. B. Crowther, who supplemented the often quoted observations of Dr George Bennett upon the habits of these animals in confinement, states: " They soon become very tame in captivity; in a few days the young ones appeared-to recognize a call, swimming rapidly to the hand paddling the water; and it is curious to see their attempts to procure a worm enclosed in the hand, which they greedily take when offered to them. I have noticed that they appear to be able to smell whether or not a worm is contained in the closed hand to which they swim, for they desisted from their efforts if an empty fist was offered." (W. H. F.; H. Sc.)
End of Article: PLATYPUS
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