154 THE BIDDLE OF THE UNIVEKSE. 



III. — The earliest metazoa with an epithelial soul : 

 the platodes. 



IV. — Invertebrate ancestors with a simple vertical 

 brain : the vermalia. 



V. — Vertebrates without skull or brain, with a 

 simple spinal chord : the acrania. 



VI. — Animals with skull and brain (of &ve vesicles): 

 the craniota. 



VII. — Mammals with predominant development of 

 the cortex of the brain : the placentals. 



VIII. — The higher anthropoid apes and man, with 

 organs of thought (in the cerebrum) : the anthro- 

 pomorpha. 



Among these eight stages in the development of the 

 human soul we may further distinguish more or less 

 clearly a number of subordinate stages. Naturally, 

 however, in reconstructing them we have to fall 

 back on the same defective evidence of empirical 

 psychology which the comparative anatomy and 

 physiology of the actual fauna affords us. As the 

 craniote animals of the sixth stage — and these are 

 true fishes — are already found fossilized in the 

 Silurian system, we are forced to assume that the 

 five preceding series of ancestors (which were 

 incapable of fossilisation) were evolved in an earlier, 

 pre- Silurian age. 



I. The cell-soul (or cytopsyche) : first stage of 

 phyletic psychogenesis. — The earliest ancestors of 

 man and all other animals were unicellular protozoa. 

 This fundamental hypothesis of rational phylogeny is 

 based, in virtue of the phyiogenetic law, on the familiar 

 embryological fact that every man, like every other 

 metazoon (i.e., every multicellular organism with 

 tissues), begins his personal existence as a simple 



