. '" . .N . 



BENNETT'S WALLABY. 



CHAPTER XXXVI 

 THE POUCHED MAMMALS OR MARSUPIALS ORDER MARSUPIALIA 



THE whole of the Mammals treated of in the preceding chapters are 

 _. collectively characterized by certain peculiarities connected with the 



istics development of their young. In all of them the young are brought 

 into the world in a more or less high state of development; this high 

 grade of development being due to the circumstance that during the greater portion 

 of intrauterine life the circulatory system of the foetus is connected with that of the 

 maternal parent by a special vascular organ termed the placenta; this placental con- 

 nection between the blood vessels of the parent and offspring allowing the blood of 

 the latter to be oxygenated almost as completely as by breathing. On account of 

 the development of this placenta, the whole of the foregoing orders of Mammals are 

 brigaded together into a single large group, or subclass, and are collectively termed 

 either Placental, or Eutherian Mammals; the latter term referring to their general 

 high degree of development, as compared with those remaining for consideration. 



On the other hand, in the Mammals of which we have to treat in the present 

 chapter, the young are born at a very early stage of development, and in an exceed- 

 ingly imperfect and helpless condition being, in fact, little more than animated 

 lumps. Previous to birth there is no placental communication between the blood 

 (1406) 



