Duckbills, except when in their burrows, pass the greater portion of their time in the water, selecting quiet pools for their favourite haunts. In such situations they may be seen on a still evening floating and diving, and looking more like bottles in the water than anything else. They obtain their food chiefly by probing in the mud with their duck-like beaks. The dwelling-chamber of the burrow is situated in the bank above the water level, but its entrance is below the surface, although there is also an exit on the land. In the pairing-season the males, which are armed with a poison-bearing spine on the inside of each hind-leg, fight fiercely among themselves. The duckbill, of which there is but a single species, is absolutely confined to southern and eastern Australia and Tasmania; and its nearest living relative is the echidna, of which a picture and notice follow. THE SPINY ANT-EATER OR ECHIDNA (_Tachyglossus aculeatus_) No one who looked at the portrait of the spiny ant-eater for the first time, and had no knowledge of its anatomy or history, would be likely to guess that it was a near relative of the duckbill. But in natural history, when we have to deal with members of different groups, externals count for very little, and all depends upon internal organisation. In the latter respect the echidnas, for there is more than one species, resemble in all essential features the duckbill, as they do in laying hard-shelled eggs, from which the young are eventually hatched. The single egg of the echidna, in place of being laid in a burrow, is, however, carried about by the female in a pouch developed for the purpose on the under side of her body shortly before the egg is laid; and in this same temporary pouch the young is likewise nurtured during the earlier stages of its existence. The duckbill and the echidna afford an excellent example of the diversity of appearance produced in animals more or less nearly related to each other by specialisation and adaptation to totally distinct modes of life. In the duckbill the specialisation and adaptation are for an aquatic existence; in the echidna they are for a burrowing, terrestrial life and a diet of ants. To an ant-eater teeth of any kind would be not only useless, but an actual hindrance, and they have accordingly been discarded, while the muzzle has been prolonged into a decidedly bird-like beak. In this respect the echidna much resembles the great South American ant-eater, which belongs to a totally different group of mammals.