42 THE EVOLUTION OF MAN. 



Skull-less Animals (Acrania), Fishes, etc., etc. On the other 

 hand, between these quite certain and most valuable phylo- 

 genetic points, great gaps in our knowledge unfortunately 

 exist, with which we shall again and again meet, and which 

 are satisfactorily explained by reasons which have already 

 been named, especially by the incompleteness of Palaeon- 

 tology, of Comparative Anatomy, and Ontogeny. 



In the first attempts to construct the human ancestral 

 line, which I. made in my Generelle Morphologie, and in 

 the "Natural History of Creation," I arranged first ten, 

 and, later, twenty-two different animal forms, which, with 

 more or less certainty, may be regarded as the animal an- 

 cestors of the human race, and which must be looked upon 

 as in a sense the most important stages of evolution in 

 the long evolutionary series from the one-celled organisms 

 up to Man.^^® Of these twenty to twenty -two animal forms, 

 about eight fall within the older division of the Inverte- 

 brates, while twelve to fourteen belong to the more recent 

 Vertebrate division. How these twenty-two most important 

 parent-forms in the human ancestral line are distributed 

 through the five main periods of the organic history of the 

 earth, is shown in the following Table (XVI.). At least half 

 of these twenty-two stages of evolution (that is, the eleven 

 oldest ancestral forms) are found within the Archilithic 

 Epoch, within that first main period of the organic history of 

 the earth, which includes the larger half of the latter, and 

 during which probably only aquatic organisms existed. The 

 eleven remaining parent-forms fall within the four remaining 

 main Epochs : three within the Paljeolithic Epoch, three 

 within the Mesolithie Epoch, and four within the CEenolithic 

 Epoch. In the last, the Anthropolithic Age, Man already 

 existed. 



