PROTOTHERIA, 



719 



many ways the copulatory organ of certain Reptiles and 

 Birds. 



The ova are large, with abundant yolk, and undergo 

 meroblastic segmentation. The Prototheria are oviparous. 



The duckmole, or duck-billed platypus, lives beside lakes and rivers. 

 It swims by means of its fore-limbs, which are webbed as well 

 as clawed ; it grubs for aquatic insects, crustaceans, and worms, in 

 the mud at the bottom of the water. It collects small animals in its 



v 



FIG. 353. Urogenital organs 

 of male duckmole. After 

 Owen. 



/?/., Bladder; u., ureter; e'.</., vas 

 deferens ; ;'. , rectum ; gl., gland ; cl., 

 cloaca ; /., penis ; u.g.c., urogenital 

 canal. 



ut 



u.) 



cl 



FIG. 354. - - Urogenital organs 

 of female duckmole, After 

 Owen. 



Ov., Ovary ; od., oviduct ; od'. , internal 

 opening of oviduct; ut., "uterine" 

 region; iff., opening of "uterine" 

 region into sinus; u., ureter; r., 

 rectum ; uv. , bladder ; Kg. , uro- 

 genital sinus ; cl., cloaca. 



cheek pouches, and chews them at leisure with its eight horny jaw- 

 plates. It makes long burrows in the banks, often with two openings, 

 one above, one under the water. The animal is shy, and dives swiftly 

 when alarmed. "When about to sleep, it rolls itself into a ball. In the 

 recesses of the burrows the eggs are laid, two at a time. The egg 

 measures about three-quarters of an inch in length, and is enclosed in a 

 "strong, flexible, white shell," through which the young animal has to 

 break its way. 



The full-grown duckmole measures from 18 to 20 in. in length ; 

 the male slightly exceeds his mate. The fur is short and soft, 

 dark-brown above, lighter beneath. The jaws are flattened like the 



