248 THE HISTORY OF CREATION. 



as in most cases, preferred the monophyletic, or one-rootetl, 

 to the polyphyletie, or many-rooted, hypothesis of descent. 

 I assumed that all Placental animals were derived fi'om 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, etc. 

 As we do not at present possess sufficient empiric material 

 to solve this most difficult qTiestion, we must leave it and 



