252 POUCHED MAMMALS OR MARSUPIALS. 



feeders have teeth with constantly growing roots like 

 those of the Rabbits. In the insect and flesh eating 

 pouched mammals the roots of the teeth do not increase; 

 and the canine teeth, which are well developed in the 

 carnivorous forms of the order, are absent or very much 

 reduced in the vegetable feeders. It is also worthy of 

 notice that, with the exception of the Wombat, most of 

 the Marsupials have an unequal number of incisor teeth 

 in the upper and lower jaw. The premolars are double 

 fanged and are usually -f on each side. The com- 

 monest formula for the true grinders is I, but in the 

 Banded Ant Eater it rises to f and in the flying Pha- 

 langer falls to t. In the Kangaroos the mode of suc- 

 cession of the teeth is singular, the hinder ones eventu- 

 ally replacing in function those in front as the latter 

 become worn away. i 



"The stomach also varies in shape with the food, being 

 simply oval or rounded in the carnivorous or insectivorous 

 forms, while in the herbivorous kangaroos it is converted 

 into a gut-like tube,, sacculated like the colon, sometimes 

 as long as the body, and occasionally provided, near the 

 entrance of the gullet, with two blind sack-like append- 

 ages. 



"The most preposterous theories as to the mode of 

 development of the kangaroos were at one time credited 

 by the Australian colonists and even by naturalists. It 

 was thought that the young were formed at the end of 

 the teat, and indeed the intimate connection which 

 exists between the teat and the young readily explains 

 such a popular conception. Now, however, ripe embryos 

 have been discovered in the uteri, and such have also 

 been observed a few hours after their fixation to the 

 teats. There appears to be no doubt that the trans- 

 ference of the young from the womb to the pouch is 

 effected by the mother's lips, the fore-paws being only 

 employed to hold the lips of the pouch widely open. 

 Both transference and fixation are, however, difficult to 

 observe, for the little embryo, hardly an inch long, is 

 first concealed by the lips of the mother, and then more 

 effectually so by the insertion of the mother's head into 

 the pouch. Even in the largest member of the family, 

 the giant kangaroo, the young, when born, are no larger 



