412 THE EVOLUTION OF MAN. 



come the highest Vertebrates, in which the middle and the 

 older stages of ancestral evolution have been either falsified 

 or abridged, but in which the later stages of the phylo- 

 genetic process are still well retained in the Ontogeny. 

 Thus it is possible, by collating and comparing the history 

 of individual development in the different groups of Verte- 

 brates, to obtain an approximately complete picture of the 

 palseontological history of the development of the ancestors 

 of Man, within the vertebrate tribe. If we descend below 

 the lowest Vertebrates, and compare the germ-history of 

 these with that of the phylogenetically allied Invertebrates, 

 we can trace the genealogical line of our animal ancestors 

 much further, as far back as the lowest Plant-animals 

 {Zoophytes) and Primitive-animals {Protozoa). 



In now treading the obscure path of this phylogenetic 

 labyrinth, holding fast the Ariadne's clew of the funda- 

 mental law of Biogeny and guided by the light of Com- 

 parative Anatomy, we must, in accordance with the method 

 we have just indicated, search out from among the diverse 

 germ-histories of very different animals, those fragments from 

 which we may construct the tribal history of Man ; and we 

 must arrange these fragments in their proper order. Here 

 again I would call special attention to the fact that we 

 employ this method with the same certainty and with the 

 same right as do geologists. No geologist has seen the 

 actual process in which the gigantic rock-masses, composing 

 the Carboniferous formations, the Jurassic, the Cretaceous, 

 etc., were actually deposited by the water. Nor has any 

 geologist actually seen that these various sedimentary rocky 

 formations originated in a particular sequence ; and yet all 

 agree as to this sequence. The reason of this is that only 



