29 



In philosophy : — 



" A change from an indefinite, incoherent homo- 

 geneity, to a definite, coherent heterogeneity, 

 through continuous differentiation and integra- 

 tion." Spencer (First Principles). 



In biology : — 



As applied to the origin of the individual, — 



" The becoming perceptible of preexisting 

 latent diversities," Roux. (See above, VI, 2.) 



As applied to the origin of species, — 



Descent with modification from preexisting 

 species. 



The theory of organic evolution stated. 



iv. The Evidence of Organic Evolution. 



(Romanes, Darwin and after Darwin, Vol. i,pp. 23-248; Spen- 

 cer, Principles of Biology, Vol. I, pp. 346-401 ; Wallace, 

 On the Law which has Regulated the Introduction of New 

 Species, Annals and Magazine of Natural History, Sept. 1855, 

 (Ser. 2), Vol. 16, p. 184; Fritz Muller, Fiir Darwin, 1864, 

 see also Trans., Facts and Arguments for Darwin, 1869 ; 

 Wiedersheim, Structure of Man, 1895.) 



1. The evidence from Classification. 



Failure of the linear arrangement. 



True relations shown only by tree-like arrange- 

 ment, e. g. Scyphomedusae. 



This arrangement best explained by evolution. 



Gradations of species into one another. 



Calcareous sponges. 



2. The evidence from Geographical Distribution. 



The continuous distribution of a species. 



Distribution of the species in a genus often dis- 

 continuous. 



