COMMON ORIGIN OF PLANTS AND ANIMALS, ca 
consequently upon differences in their capability of develop- 
ment. A small number of Monera would then have given 
origin to the animal kingdom, and, again, a small number 
would have produced the vegetable kingdom. Between these 
two groups, however, there would have developed, indepen- 
dently of them, a large number of independent tribes, which 
have remained at a lower stage of organization, and which 
have neither developed into genuine plants nor into genuine 
animals, 
A safe means of deciding between the monophyletic and 
olyphyletic hypotheses is as yet quite impossible, consider- 
ing the imperfect state of our phylogenetic knowledge. The 
different groups of Protista, and those lowest forms of the 
animal kingdom and of the vegetable kingdom which are 
scarcely distinguishable from the Protista, show such a close 
connection with one another and such a confused mixture 
of characteristics, that at present any systematic division 
and arrangement of the groups of forms seem more or 
less artificial and forced. Hence the attempt here offered 
must be regarded as entirely provisional. But the more 
deeply we penetrate into the genealogical secrets of this 
obscure domain of inquiry, the more probable appears the 
idea that the vegetable kingdom and the animal kingdom 
are each of independent origin, and that midway between 
these two great pedigrees a number of other independent 
small groups of organisms have arisen by repeated acts of 
spontaneous generation, which on account of their indifferent 
neutral character, and in consequence of their mixture of 
animal and vegetable properties, may lay claim to the 
designation of independent Protista. 
Thus, if we assume one entirely independent trunk for 
