356 ORNITHORHYNCUS. 



the cheek-pouches. The animals usually remain at the surface 

 of the water, with the head slightly raised above it ; but upon 

 the slightest alarm they instantl} disappear ; and they are so 

 watchful of danger, that the mere act of levelling a gun is 

 sufficient to cause them to dive. After some little time, they 

 reappear at some distance from the spot where they sank. Their 

 burrows are excavated in the banks of the streams they inhabit, 

 and are of very curious construction. The entrance is situated 

 near the water's edge, on a steep part of the bank ; and is con- 

 cealed amongst the herbage. It gradually rises from the level of 

 the stream, proceeding in a serpentine direction to a distance of 

 twenty or even fiftj feet from the entrance ; and its termination 

 is enlarged, so as to form a kind of nest for the parents and their 

 offspring, which is strewed with dry river-weed. The burrows 

 have usually a second orifice, below the surface of the water ; 

 communicating with the passage just within the upper entrance. 

 319. The young are produced in a very imperfect state, and 

 are very unlike the fully-developed animal. The skin is entirely 

 destitute of fur, and is thrown, by the curling of the body, and 

 the doubling of the head and tail beneath it, into transverse 

 folds ; the eyes are not formed, and their place is merely indicated 

 by the presence of a few wrinkles on the skin. The margin of 

 the bill is at that time soft, and the tongue (which in the adult 

 does not extend between the mandibles) advances to its front 

 edge ; so that the young animal can obtain nourishment by 

 sucking, which was at first thought impossible. The mammary 

 gland of the female is very simple in structure, and is divided 

 into a large number of separate lobes ; this is just what might 

 be expected, when it is remembered that the organ here makes 

 its first appearance, and presents therefore its lowest grade of 

 formation ( ANIM. PHYSIOL., 358). The Ornithorhyncus is truly 

 ovo- viviparous ; for the embryo appears never to derive any 

 other sustenance from its parent, up to the time of its birth, than 

 that which is stored up for it in the ovum ; but, as in some 

 Lizards and Fishes, the egg is hatched (as it were) within t 

 oviduct, so that the young is born alive. In consequence of i 

 ' imperfect condition, however, it cannot leave its burrow or 



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