40 THE EVOLUTION OF MAN. 



struggle for existence has excited an equally strong modify- 

 ing influence upon the various independent and yet un- 

 developed young forms, as upon the developed and mature 

 forms. Therefore, in the Ontogeny of the higher animal 

 forms, the Phylogeny has been very greatly limited by Keno- 

 genesis ; as a rule, only a blurred and much vitiated picture 

 of the original course of evolution of their ancestors now 

 lies before us in the Ontogeny. Only with great precaution 

 and judgment dare we infer the tribal history directly from 

 the germ-history. Moreover, the germ-history itself is 

 known to us only in the case of very few species. 



Lastly, the highly important record of creation afforded 

 by Comparative Anatomy is unfortunately very incomplete, 

 and for the simple reason, that the number of extant 

 animal species forms but a very small fragment of the 

 whole number of different animal forms that have existed 

 from the beginning of the organic history of the world to 

 the present time. The total sum of the latter may safely 

 be estimated at several millions. The number of those 

 animals the organization of which has at present been 

 investigated by Comparative Anatomy is very small in pro- 

 portion. The more extended investigations of the future 

 will, here also, open up unexpected treasures. 



In view of this evident and natural incompleteness of 

 the most important records of creation, we must of course 

 take good care, in the tribal history of Man, not to lay too 

 great weight on single known animal forms, nor with equal 

 certainty to consider all the stages of evolution which come 

 under our consideration, as parent-forms. On the contrary, 

 in hypothetically arranging our ancestral line, we must 

 take good care to remember that the single hypothetical 



