Permanence and Evolution. 9 



breeding with one another, as Darwin points 

 out (" Origin of Species," Edition IV., p. 302, et 

 seq.\ It is, then, rash to feel sure that the 

 difference between races which will not cross, not 

 only so as to produce sterile offspring, is deeper 

 or more fundamental than that between some 

 which produce fertile crosses, for it may be that 

 it only happens to affect the reproductive 

 system and not any other part of the organism. 

 Even granting it is more fundamental, it does 

 not follow that permanence of type is less 

 absolute in the one case than in the other. 

 Most of the disputes there have been as to the 

 specific unity of different animals arise out of 

 the appropriation of parts of the definition of 

 species by naturalists, who have ignored the 

 remaining parts. 



For instance, when De Blainville (" Os- 

 teographie") found that the differences be- 

 tween the several Eastern forms of wild hog 

 were small compared with what he was ac- 



