Chap. XlII. 
CLxiSSIFICATION. 
423 
it would connect together all languages, extinct and 
modern, by the closest affinities, and would give the 
filiation and origin of each tongue. 
In confirmation of this view, let us glance at 
the classification of varieties, which are believed or 
known to have descended from one species. These 
are grouped under species, with sub-varieties under 
varieties; and with our domestic productions, several 
other grades of difference are requisite, as we have 
seen with pigeons. The origin of the existence of 
groups subordinate to groups, is the same with varieties 
as with species, namely, closeness of descent with various 
degrees of modification. Nearly the same rules are fol¬ 
lowed in classifying varieties, as with species. Authors 
have insisted on the necessity of classing varieties on a 
natural instead of an artificial system; we are cau¬ 
tioned, for instance, not to class two varieties of the 
pine-apple together, merely because their fruit, though 
the most important part, happens to be nearly identical; 
no one puts the Swedish and common turnips 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 Mar¬ 
shall says the horns are very useful for this purpose 
with cattle, because they are less variable than the 
shape or colour of the body, &c.; whereas with sheep 
the horns are much less serviceable, because less con¬ 
stant. In classing varieties, I apprehend if we had a 
real pedigree, a genealogical classification would be 
universally preferred; and it has been attempted by 
some authors. Eor we "night feel sure, whether there 
had been more or less modification, the principle of 
inheritance would keep the forms together which were 
allied in the greatest number of points. In tumbler 
pigeons, though some sub-varieties differ from the others 
