158 GEOLOGICAL BIOLOGY. 



gories of Ontogeny and Phylogeny. Ontogeny, or Ontogenesis, 

 is the technical term for the " history of the individual devel- 

 opment of the organized being." Phylogeny is applied to the 

 history of the genealogical development. Phylogeny, as 

 Haeckel used it, is associated with the theory * that the steps 

 of phylogenesis, or of ancestral development, may be deduced 

 from the observed history of ontogenesis or the development 

 of the individual. In order to free the term from any theory 

 of accounting for the history, it is proposed to restrict the use 

 of the term evolution to that part of the history of organisms 

 which is seen upon comparing the organisms of one geological 

 epoch with those most closely similar in the preceding geo- 

 logical epochs, and to restrict the use of the term develop- 

 ment to the history of those changes which are observed on 

 comparing the successive stages of growth of the individual 

 organism with each other, or the history of a single cycle of 

 organic growth. 



Evolution the History of the Steps by which Variation is Ac- 

 quired, not Transmitted. — It is evident from this analysis that 

 in the case of any particular organism the steps by which it 

 acquires the characters which were possessed by its parents 

 are steps in the development of the individual ; but the steps 

 by which it acquires any characters not possessed by its ances- 

 tors are steps of evolution. The latter characters in every 

 case are the varietal characters. 



It is the acquirement of variation, not its transmission, that 

 constitutes whatever there is of evolution in the history of 

 organisms. The terms thus restricted furnish us with names 

 which can be used independently of any theory. The facts, 

 or series of facts, may be scientifically observed, recorded, and 

 defined, and an explanation sought for them. 



A Definition of Darwinism. — For the meaning of Darwinism 

 we may adopt the excellent definition of the Century Diction- 

 ary. " That which is specially and properly Darwinian, in 



* The Recapitulation theory. See, for a clear statement of the principal 

 features of this theory, the President's address to the Biological Section of the 

 British Association, delivered at Leeds, September 1890, by Arthur Milnes Mar- 

 shall, entitled "The Recapitulation Theory," and republished in "Biological 

 Lectures and Addresses," 1894, pp. 2S9-363. 



