224 THE OlilOhy OF SPECIES 



groups; but tho proper or even the only possible ar 

 rjuigemeut would still bo genealogical; and tliis would 

 be strictly natural, as it would connect together all lan- 

 guages, extinct and recent, by the closest affinities, and 

 would give the liliation and origin of each tongue. 



In confirmation of this view, let ns glance at the 

 classiticatiou of varieties, which are known or believed 

 to be descended from a single species. These are 

 grouped under the species, with the sub- varieties under 

 Ihe varieties: and iu some cases, as with the domestic 

 pigeon, with several other grades ot* difference. Nearly 

 the same rules are followed as in classifying species. 

 Authors have insisted on the necessity of arranging vari- 

 eties on a natural instead of an artificial s^'stem; we are 

 cautioned, for instance, not to class two varieties of the 

 pineapple together, merely because their fruit, though 

 the most important part, happens to be nearly identical; 

 no one puts the Swedish and common turnip together, 

 though the esculent and thickened stems are so similar. 

 Whatever part is found to be most constant is used in 

 classing varieties: thus the great agriculturist Marshall 

 says the horns are very useful for this purpose with 

 cattle because they are less variable than the shape or 

 color of tne body, etc. ; whereas with sheep the horns are 

 much less serviceable, because less constant. In class- 

 ing varieties I apprehend that if we had a real pedigree, 

 a genealogical classification would be universally pre- 

 ferred; and it has been attempted in some cases. For 

 we might feel sure, whether there had been more or less 

 modification, that the principle of inheritance would keep 

 the forms together which were allied m the greatest 

 number of points. Iu tumbler pigeons, though some of 



