492 



MANUAL OF ZOOLOGY. 



later stage the young can suckle by their own exertions, and 

 they leave the pouch and return to it at will. In a few forms 

 there is no complete marsupium as above described ; but the 

 structure of the nipples is the same, and the young are carried 

 about by the mother, adhering to the lengthy teats. 



The so-called "marsupial bones" (fig. 187) doubtless serve 

 to support the marsupial pouch and its contained young, but 

 this cannot be their sole function, 

 since they occur in the Monotremes, 

 in which there is no pouch. 



The oviducts open into vaginal 

 tubes which open into a urogenital 

 canal; but this does not open into 

 a " cloaca," though embraced by a 

 sphincter muscle common to it and 

 to the rectum. The testes are not 

 abdominal throughout life as in the 

 Monotremes, but are lodged in a 

 scrotum. This, however, is placed in 

 front of the penis, and not beneath 

 the pubic arch as in most Mammals. 

 From this unusual position of the 

 scrotum, it is regarded by Owen as 

 being the same structure as the mar- 

 supial pouch of the female, turned 

 inside out. Though they form an 

 extremely natural order, sharply sep- 

 arated from all the rest of the Mam- 

 mals, the Marsupials form a large and 

 varied group. In fact this order, from 

 being the almost exclusive possessor of a continent as large 

 as Australia, has to discharge in the economy of nature func- 

 tions which are elsewhere discharged by several orders. 



The Marsupialia are divided by Owen into the following 

 sections : 



a. Rhizophaga. In this section is the well-known Australian 

 animal, the Wombat (Phascolomys fossor\ often called by the 

 colonists the "badger." The Wombat is a stout, heavy 

 animal, which attains a length of from two to three feet. The 

 legs are very short and stout, and the animal burrows with 

 ease by means of strong curved digging-claws, with which the 

 fore-feet are furnished. The tail in the Wombat is quite 

 rudimentary, and the whole body is clothed with a brown 

 woolly hair. In its dentition the Wombat presents a curious 

 resemblance to the herbivorous Rodents, There are two 



Fig. 187. One side of the pelvis 

 of a Kangaroo, showing the 

 " marsupial bones " (m) 

 after Owen. 



