THE ORIGIN OF SPECIES. 17 



theory brings us the other way to the same result. In 

 his view, not only all the individuals of a species are 

 descendants of a common parent, but of all the related 

 species also. Affinity, relationship, all the terms which 

 naturalists use figuratively to express an underived, 

 unexplained resemblance among species, have a literal 

 meaning upon Darwin's system, which they little sus- 

 pected, namely, that of inheritance. Varieties are the 

 latest offshoots of the genealogical tree in " an un- 

 lineal " order ; species, those of an earlier date, but of 

 no definite distinction ; genera, more ancient species, 

 and so on. The human races, upon this view, like- 

 wise may or may not be species according to the 

 notions of each naturalist as to what differences are 

 specific ; but, if not species already, those races that 

 last long enough are sure to become so. It is only a 

 question of time. 



How well the simile of a genealogical tree illus- 

 trates the main ideas of Darwin's theory the following 

 extract from the summary of the fourth chapter shows : 



" It is a truly wonderful fact the wonder of which we are 

 apt to overlook from familiarity that all animals and all plants 

 throughout all time and space should be related to each other 

 in group subordinate to group, in the manner which we every- 

 where behold namely, varieties of the same species most 

 closely related together, species of the same genus less closely 

 and unequally related together, forming sections and sub-genera, 

 species of distinct genera much less closely related, and genera 

 related in different degrees, forming sub-families, families, or- 

 ders, sub-classes, and classes. The several subordinate groups 

 in any class cannot be ranked in a single file, but seem rather 

 to be clustered round points, and these round other points, and 

 so on in almost endless cycles. On the view that each species 

 has been independently created, T can see no explanation of this 



