454 The Outline of Science 



rapidly with very strong claws. They seem almost to sink into 

 the ground. When they get among rough herbage they take 

 firm hold with their feet and are very difficult to dislodge. The 

 snout is prolonged into a slender tube, through which a mobile, 

 sticky, worm-like tongue is protruded on the ants which form 

 the staple food. No traces of teeth are to be seen, even in the 

 embryo. As in the Duckmole, the male has a well-developed 

 spur on the hind-leg, perforated by the duct of a gland, but its 

 use is obscure. The egg seems to be placed by the mother in a 

 temporarily developed pouch, which is said to be comparable to 

 a greatly enlarged teat of the type seen in the cow. Within 

 this pouch the milk oozes out. There are no stranger animals 

 in existence than the Duckmole and the Spiny Ant-eaters. They 

 might almost be called "living fossils." 



2 



The Pouch-bearing Mammals 



The second grade among present-day mammals is that of 

 the Marsupials, which are now confined to Australia except in 

 the case of two families the American Opossums and Selvas. 

 In most cases the female has a pouch or marsupium developed 

 around the mammas, and in this pocket the prematurely born 

 young are stowed away and carried about till they are able to 

 fend for themselves. In many opossums the pouch is absent, 

 and the mother carries the young ones on her back, with their 

 tails coiled round hers a quaint device. In marsupials in gen- 

 eral, the young ones are born very helpless, unable even to suck. 

 The mother takes her young one in her mouth, and puts it into 

 her skin-pouch, within which lie the teats or mamma?. The 

 mother adjusts matters so that the mouth of the young one closes 

 on a teat, which then swells a little, and, as the prematurely born 

 offspring cannot suck, she injects the milk down the gullet by 

 contracting a special musculature. The milk might "go down 

 the wrong way" and choke the offspring, were it not that the 



