16 DARWINIANA. 



In tlie first place, tliey practically agree in upset- 

 ting, each in its own way, the generally-received defi- 

 nition of species, and in sweeping away the ground of 

 their objective existence in ^Nature. The orthodox 

 conception of species is that of lineal descent : all the 

 descendants of a common parent, and no other, con- 

 stitute a species ; they have a certain identity because 

 of their descent, by which they are supposed to be 

 recognizable. So naturalists had a distinct idea of 

 what they meant by the term species, and a practical 

 rule, which was hardly the less useful because difficult 

 to apply in many cases, and because its application was 

 indirect : that is, the community of origin had to be 

 inferred from the likeness ; such degree of similarity, 

 and such only, being held to be conspecific as could 

 be shown or reasonably inferred to be compatible with 

 a common origin. And the usual concurrence of the 

 whole body of naturalists (having the same data be- 

 fore them) as to what forms are species attests the 

 value of the rule, and also indicates some real founda- 

 tion for it in Nature. But if species were created in 

 numberless individuals over broad spaces of territory, 

 these individuals are connected only in idea, and spe- 

 cies differ from varieties on the one hand, and from 

 genera, tribes, etc., on the other, only in degree ; and 

 no obvious natural reason remains for fixing upon this 

 or that degree as specific, at least no natural standard, 

 by which the opinions of different naturalists may be 

 correlated. Species upon this view are enduring, but 

 subjective and ideal. Any three or more of the hu- 

 man races, for example, are species or not species, ac- 

 cording to the bent of the naturalist's mind. Darwin's 



