THE WATER-MOLE. 



217 



monotremes lay eggs similar to those of rep- 

 tiles and birds. * These eggs have a thin but 

 yet calcareous shell and are carried about for 

 a time in a depression of the skin. Into this 

 depression open several canals belonging to 

 glands which secrete milk and which accor- 

 dingly are true milk-glands, but which form 

 no projecting teats. In the duck-mole the 

 egg-pouch forms a longish fold of the skin, 



which, after the escape of the young one 

 from the egg, becomes so reduced as to be 

 scarcely recognizable, and is seized hold of 

 by the young one with its broad beak in 

 sucking. The young of the echidna, on the 

 other hand, is lodged in a round brood-pouch, 

 in which it buries its head with its still short 

 beak, seizing hold of the bottom of the pouch 

 along with the gland openings which are 



Fig. 264.— The Water-mole or Duck-mole {Ornithorhynchus paradoxus) 



found there. Here, accordingly, we see a 

 transition to the formation of a complete 

 marsupial pouch. 



Concerning the development of the young 

 in the egg we possess so far no observations. 

 In any case they escape from the egg while 

 still in a very imperfect state of development. 

 The youngest specimens which have been 

 found were still without hair, the eyes were 

 closed and concealed by the skin; on the 

 short limbs the five toes are, however, already 

 recognizable, and in the males also the spur. 

 The beak of these young ones is very short, 

 in the duck-mole roundish, in the echidnas 

 more elongated. The large thick tongue 

 reaches to the point of the beak and ap- 

 parently plays in sucking the part of a 

 piston. 



The two genera forming this order are so 

 different in their bodily structure that they 



Vol. II. 



must be regarded as representatives of dif- 

 ferent families. 



The Water-Mole, Duck-mole, or Duck-billed 

 Platypus. 



This, the sole known species {Ornithorhyn- 

 chus paradoxus), fig. 264, is a native of 

 Southern Australia and Tasmania. It may 

 attain a length of about 20 inches, and pre- 

 sents a very singular appearance. The body 

 is rather long, compact, and almost every- 

 where of the same thickness. It rests on 

 short massive legs, and carries a flat broad 

 tail, which is only slightly covered with hair, 

 and that only on the under side. The body, 

 which resembles that of the sea-otter, is 

 covered with a short, thick, gray down inter- 

 spersed with numerous coarse hairs of a 

 brown colour, these hairs being pretty long 

 on the back, where they almost form a sort 



60 



