248 THE HISTORY OF CREATION. 
as in most cases, preferred the monophyletic, or one-rooted, 
to the polyphyletic, or many-rooted, hypothesis of descent. 
I assumed that all Placental animals were derived from a 
single form of Marsupial animal, which, for the first time, 
began to form a placenta. In this case the Villiplacentals, 
Zonoplacentals, and Discoplacentals would perhaps have to 
be considered as three diverging branches of the common 
primary form of Placentals, or it might also be conceived that 
the two latter, the Deciduata, had developed only at a later 
period out of the Indeciduata, which on their part had 
arisen directly out of the Marsupials. However, there are 
also important reasons for the alternative; namely, that 
several groups of Placentals, differing from the beginning, 
arose out of several distinct groups of Marsupials, so that 
the placenta itself was formed several times independently. 
This opinion is maintained by Huxley, the most eminent 
English zoologist, and by many others. In this case the 
Indeciduata and the Deciduata would perhaps have to be 
considered as two completely distinct groups; then the 
order of Hoofed animals, as the primary group of the 
Indeciduata, might be supposed to have originated out 
of the Marsupial hoofed animals (Barypoda). Among the 
Deciduata, on the other hand, the order of Semi-apes, as the 
common primary form of the other orders, might possibly 
have arisen out of Handed Marsupials (Pedimana). But it 
is also conceivable that the Deciduata themselves have arisen 
out of several different orders of Marsupials, Animals of Prey 
out of Rapacious Marsupials, Gnawing animals out of Gnaw- 
ing Marsupials, Semi-apes out of Handed Marsupials, ete. 
As we do not at present possess sufficient empiric material 
to solve this most difficult question, we must leave it and 
