244 THE HISTORY OF CREATION. 
directly allied to the Semi-apes, or Prosimia, among Placental 
animals. It is possible that these latter are really next 
akin to the marsupials with hands, and that they have 
developed out of their long since extinct ancestors. 
It is very difficult to discover the genealogy of Marsupials, 
and this more especially because we are but very imperfectly 
acquainted with the whole sub-class; and the Marsupials of 
the present day are evidently only the last remnants of a 
group that was at one time rich in forms. It is possible 
that Marsupials with hands, those with snouts, as well as 
rapacious Marsupials, developed as three diverging branches 
out of the common primary group of Primeval Marsupials. 
Tn a similar manner, on the other hand, the rodent, leaping, 
and hoofed Marsupials have perhaps arisen as three diverging 
branches out of the common herbivorous primary group, 
that is, out of the Climbing Marsupials. Climbing and 
Primeval Marsupials might, however, be two diverging 
branches of the common primary forms of all Marsupials, 
that is, of the Primary Marsupials (Prodidelphia), which 
originated during the older secondary period out of Cloacal 
animals. 
The third and last sub-class of mammals comprises the 
Placental animals, or Placentals (Monodelphia, or Placen- 
talia). 1t is by far the most important, comprehensive, and 
most perfect of the three sub-classes; for the class includes 
all the known mammalia, with the exception of Marsupials 
and Beaked animals. Man also belongs to this sub-class, 
and has developed out of its lower members. 
Placental animals, as their name indicates, are distin- 
guished from all other mammals, more especially by the 
formation of a so called placenta. This is a wery peculiar 
