REVERSION. l6g 



modes of heredity have been defined by Darwin, 

 and yet more systematically by Hacckel, as "laws of 

 inheritance," and corroborated by them by a prcfu- 

 sion of examples. If heredity may be termed the 

 conservative element in the life of species, we may also 

 speak in particular of a conservative heredity, by 

 which the old, long-established characteristics and pe- 

 culiarities are transferred. The more stubbornly a 

 character is transmitted, or, what amounts to tlie same, 

 the greater the number of families, genera, and species, 

 over which a character. is extended, the more ancient 

 must it be considered, the earlier did it appear in the 

 ancestral stock. In most cases, this conservative he- 

 redity occurs in an unbroken succession of generations, 

 an observation on which it is needless to enlarge, 

 as it may be daily made by every one. But con- 

 servative heredity may likewise display itself inter- 

 mittently, either when merely individual characters of 

 the ancestors reappear after lying dormant for one, 

 several, or many generations, — a phenomenon desig- 

 nated as Atavism, or reversion, — or when the species 

 is composed of a regular alternation of variously con- 

 stituted generations and individuals. This particular 

 sort of reversion is termed Alternate Generation, or 

 Heterogenesis. 



No one is surprised if children exhibit the bodily 

 or mental features of their grand-parents which were 

 suspended in the parents. But most frequent and 

 striking is the atavism of domestic animals and culti- 

 vated plants, a stubborn antagonist to breeders. Of no 

 domestic animal is the aboriginal stock known with such 

 approximate certainty as that of the pigeon. Now there 



