46 THE HISTORY OF CREATION. 
some zoologists will be more in favour of the supposition 
that: all placental animals are derived from a single pouched 
animal; others will be more in favour of the opposite sup- 
position, that several different groups of placental animals 
have proceeded from several different pouched animals, In 
regard to the human race itself, some will prefer to derive 
it from a single form of ape, while others will be more 
inclined to the tdea that several different races of men have 
arisen, independently of one another, out of several different 
species of ape. Without here expressing our opimion in 
favour of either the one or the other conception, we must, 
nevertheless, remark that in general the monophyletic 
hypothesis of descent deserves to be preferred to the 
polyphyletic hypothesis of descent. In accordance with the 
chorological proposition of a single “centre of creation” 
or of a single primzeval home for most species (which has 
already been discussed), we may be permitted to assume 
that the original form of every larger or smaller natural 
croup only originated once in the course of time, and only 
in one part of the earth. We may safely assume this 
simple original root, that is, the monophyletic origin, in the 
case of all the more highly developed groups of the animal 
and vegetable kingdoms. (Compare vol.i. p. 353). But it is 
very possible that the more complete Theory of Descent of 
the future will involve the polyphyletic origin of very 
many of the low and imperfect groups of the two organic 
kingdoms. 
For these reasons I consider it best, in the mean time, to 
adopt the monophyletic hypothesis of descent both for the 
animal and for the vegetable kingdom. Accordingly, the 
above-mentioned six tribes, or phyla, of the animal kingdom 
