MARSUPIALIA. 253 



than a newly-born mouse. It is interesting to compare the 

 degree of development of the hind and fore legs at this 

 stage. While in the fore feet the five fingers are distinctly 

 formed, even to the tips of the claws, the hind feet are 

 more like short fins slightly notched into three lobes, the 

 inner of which is again perceptibly divided, in correspond- 

 ence with the structure of the adult foot. One of the most 

 remarkable features about the young kangaroo is the 

 largely-developed mouth and tongue; by their aid the 

 little creature is able to grasp the teat firmly, and in 

 fact the orifice of the mouth may grow smaller after the 

 teat has once been firmly secured in it. The milk is 

 injected into the gullet of the young, passing on each 

 side of the upper end of the windpipe which is carried 

 as far up as the hinder part of the nasal cavity. In 

 this way the little creatures may breathe, and be fed at 

 the same time, without danger of choking. The injec- 

 tion of the milk is effected by a specially modified part, 

 the cremaster, of one of the superficial abdominal mus- 

 cles. The epipubic, or so-called marsupial bones, serve 

 as a sort of pulley by which the cremaster muscles are 

 enabled more effectively to compress the milk glands. 



"The duration of the pouch-life of the young varies 

 with the species. The Kangaroo, according to Owen, 

 suckles her young for eight months. During this period 

 the hind legs and tail assume a great part of their adult 

 proportions; the muzzle elongates, the external ears and 

 eyelids are completed, and the hair begins to develop 

 about the sixth month ; at the eighth the young kangaroo 

 may be seen frequently to protrude its head from the 

 mouth of the pouch, and to crop the grass at the same 

 time that the mother is browsing. Having thus acquired 

 additional strength it quits the pouch, and hops at first 

 with a feeble and vacillating gait, but continues to 

 return to the pouch for occasional shelter and supplies 

 of food till it has attained the weight of ten pounds; 

 after this it w r ill occasionally insert its head for the pur- 

 pose of sucking, notwithstanding another foetus may have 

 been deposited in the pouch, for the latter attaches itself 

 to a different nipple from the one which had been used 

 'by its predecessor. 



