PREFACE TO THE THIRD EDITION. 



Heutigen Entwickelungsgeschichte "). The celebrated 

 theories of His, of which I have spoken as the " envelope 

 theory," "gum-pouch theory," "waste-rag theory," etc., 

 are the brilliant results of that " gifted " author's efforts 

 and mathematical calculations. And yet many have 

 allowed themselves to be dazzled by the " exact " appear- 

 ance of his mathematical formula The history of the 

 evolution of organisms, equally with the history of human 

 civilization, can never be the subject of " exact " investi- 

 gation. The history of evolution is in its very nature an 

 historic natural science, as is geology. To regard and 

 treat these and other historic natural sciences as " exact " 

 leads to the greatest errors. This is as true of germ- 

 history (Ontogeny) as of tribal history (Phylogeny) ; foi 

 between the two there is the most intimate causal 

 connection. 



Many naturalists have especially blamed the diagram- 

 matic figures given in the Anthropogeny. Certain tech- 

 nical embryologists have brought most severe accusations 

 against me on this account, and have advised me to substi- 

 tute a larger number of elaborated figures, as accurate as 

 possible. I, however, consider that diagrams are much 

 more instructive than such figures, especially in popular 

 scientific works. For each simple diagrammatic figure 

 gives only those essential form-features which it is intended 

 to explain, and omits all those unessential details which in 

 finished, exact figures, generally rather disturb and confuse 

 than instruct and explain. The more complex are the 

 form-features, the more do simple diagrams help to make 

 them intelligible. For this reason, the few diagrammatic 

 figures, simple and rough as they were, with which Baer 



