58 GEOLOGICAL PERIODS. 



evolved : in one direction the lower groups of 

 Zoophytes, and in another Worms. It is among the 

 Worms that the stem of Echinodermata, Mollusca, 

 Arthropoda, and Vertebrata is to be found ; but in 

 Haeckel's opinion, there is no relationship except 

 this remote one of common descent from Worms 

 between the Vertebrata and the three other sub- 

 kingdoms mentioned. The vertebrata, he considers 

 with Mr. Darwin, as we have seen, were evolved 

 directly from ascidian worms. So far as regards the 

 study of Anthropogenesis, therefore, both ontogenetic 

 and phylogenetic, by far the largest part of the animal 

 kingdom may be excluded ; the only stems, in fact, 

 which bear upon ANTHROPOGENESIS being Protozoa, 

 Worms, and Vertebrata. 



In entering on the consideration of the Phylo- 

 genetic branch of Anthropogenesis, a brief view of 

 the geological periods at which the various ancestral 

 forms of man were, according to Haeckel, evolved, 

 is here premised. 



The PRIMORDIAL, or ARCHOZOIC or ARCHOLITHIC 

 time, comprising the Laurentian, Cambrian, and 

 Silurian periods, is supposed to have extended over 

 many millions of years a duration longer than that 

 of all the subsequent times put together. It was in 

 the earliest period of this time that living beings 

 originited by spontaneous generation. From these 

 organisms, which were of the most simple nature, 

 sprang all the invertebrate ancestors of man, from 



