VARIATION UNDER NATURE 53 



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 incipient species 

 greater than the average are now manufacturing, 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 natur- 

 alist 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 ? Undoubt- 

 edly 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 species of the same genus. But 

 when we come to discuss the principle, as I call it, of 

 Divergence of Character, we shall see how this may be 

 explained, and how the lesser differences between 

 varieties will tend to increase into the greater differ- 

 ences between species. 



There is one other point which seems to me worth 

 notice. Varieties generally have much restricted ranges: 

 this statement is indeed scarcely more than a truism, 

 for if a variety were found to have a wider range than 

 that of its supposed parent-species, their denominations 

 ought to be reversed. But there is also reason to believe, 

 that those species which are very closely allied to 

 other species, and in so far resemble varieties, often 

 have much restricted ranges. For instance. Mr. H. C. 

 W atson has marked for me in the well-sifted London 

 Catalogue of plants (4th edition) 63 plants which are 



