CHAPTER II. 
THE MARSUPIAL ANIMALS A DISTINCT CLASS. 
In commencing the next branch of the enquiry, namely, 
by what abnormal vertebrate groups are the placental ani¬ 
mals surrounded ? I should say, in the first place, that the 
marsupials form a class, distinguished from the placentals 
by their physiology, their divisibility, and their antiquity. 
1st. Tlieir Physiology. The marsupials differ from the 
placental animals in a number of peculiarities so re¬ 
markable that it seems astonishing that naturalists have 
until lately passed them over without a notice. “The 
first of all these peculiarities is the premature production 
of their young, which are born in a state of development 
scarcely comparable to that of an ordinary foetus a few days 
after conception. Incapable of motion and hardly exhi¬ 
biting the germs of limbs and other external organs, these 
little ones attach themselves to the mammae of the mo¬ 
ther, and there remain fixed until they acquire the degree 
of development in which animals are usually born.” — 
C. R. A. The young of a kangaroo examined by Professor 
Owen twelve hours after birth “ resembled an earth worm 
in the colour and semitransparency of its integument, ad¬ 
hered firmly to the point of the nipple, breathed strongly 
