THE TRIBAL AND GERM-HISTORY OF MAN. 407 



fcion which exists between these two main branches of the 

 history of human evolution. We found that this most 

 significant causal connection was most simply expressed in 

 " the fundamental law of organic evolution," the meaning 

 and significance of which was explained in detail in the 

 first chapter. According to that first biogenetic principle, 

 Ontogeny is a short and compressed recapitulation of 

 Phylogeny. If this reproduction of tribal history were 

 always complete in germ-history, it would be an easy task 

 to re-arrange Phylogeny by using Ontogeny as a guide. 

 When any one wanted to know from what ancestors each 

 higher organism is descended, therefore also from what 

 ancestors Man is descended, and from what forms the whole 

 human race has developed, it would only be necessary to 

 trace accurately the series of forms which occur in the 

 evolution of the individual from the egg; each form occur- 

 ring in this series might then, without further trouble, be 

 regarded as the representative of an old and extinct 

 ancestral form. But, as a matter of fact, this immediate 

 translation of ontogenetic facts^ into phylogenetic concep- 

 tions is only directly allowable in the case of a com- 

 paratively small part of animals. There are, it is true, a 

 number of low. Invertebrate Animals {e.g., Plant-animals, 

 Worms, Crabs) still extant, each germ-form of which we are 

 justified in explaining, without further trouble, as the 

 reproduction, or the portrait, of an extinct parent-form. But 

 in most animals, and in Man, this is impossible, because 

 the germ-forms themselves have again been modified, and 

 have partly lost their original nature, in consequence of the 

 infinite variety in the conditions of existence. 



During the immeasurable course of the organic history 



