BENNETT’S WALLABY. 
CHAPTER XXXVI. 
The Pouched Mammals, or Marsupials. 
Order Marsupialia. 
Distinctive The whole of the Mammals treated of in the preceding chapters 
Characters. are collectively characterised by certain peculiarities connected with 
the 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 intra-uterine 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 connection 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 
exceedingly imperfect and helpless condition,—being, in fact, little more than 
