Chap. II. 
RESEMBLE VARIETIES. 
57 
stiould be ranked as species or varieties. Now Fries 
has remarked in regard to plants, and Westwood in 
regard to insects, that in large genera the amount of 
difference between the species is often exceedingly small. 
I have endeavoured to test this numerically by averages, 
and, as far as my imperfect results go, they confirm the 
view. I have also consulted some sagacious and expe¬ 
rienced observers, and, after deliberation, they concur 
in this view. In this respect, therefore, the species of 
the larger genera resemble varieties, more than do the 
species of the smaller genera. Or the case may be 
put in another way, and it may be said, that in the 
larger genera, in which a number of varieties or inci¬ 
pient species greater than the average are now manu¬ 
facturing, many of the species already manufactured 
still to a certain extent resemble varieties, for they 
differ from each other by a less than usual amount of 
difference. 
Moreover, the species of the large genera are related 
to each other, in the same manner as the varieties of 
any one species are related to each other. No natu¬ 
ralist pretends that all the species of a genus are equally 
distinct from each other; they may generally be divided 
into sub-genera, or sections, or lesser groups. As Fries 
has well remarked, little groups of species are generally 
clustered like satellites around certain other species. And 
what are varieties but groups of forms, unequally related 
to each other, and clustered round certain forms—that is, 
round their parent-species ? Undoubtedly there is one 
most important point of difference between varieties and 
species; namely, that the amount of difference between 
varieties, when compared with each other or with their 
parent-species, is much less than that between the spe¬ 
cies of the same genus. But when we come to discuss 
the principle, as I call it, of Divergence of Character, 
D 3 
