COMMON OEIGIN OP PLANTS AND ANIMALS. 73 



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 pi-oduced 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 

 polyphyletic 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 gToups 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 



