VARIATION UNDER NATURE 95 



like satellites around other species. And what are vari- 

 eties but groups of forms, unequally related to each 

 other, and clustered round certain forms — that is, round 

 their parent-sj^ecies. Undoubtedly there is one most im- 

 portant 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 prin- 

 ciple, as I call it, of Divergence of Character, we shall 

 see how this may be explained, and how the lesser dif- 

 ferences between varieties tend to increase into the greater 

 differences between species. 



There is one > other point which is 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 

 would be reversed. But there is reason to believe that 

 the species which are very closely allied to other species, 

 and in so far resemble varieties, often have much-re- 

 stricted ranges. For instance, Mr. H. C. Watson has 

 marked for me in the well-sifted London Catalogue of 

 plants (4th edition) 63 plants which are therein ranked 

 as species, but which he considers as so closely allied to 

 other species as to be of doubtful value: these 63 reputed 

 species range on an average over 6-9 of the provinces 

 into which Mr. Watson has divided Great Britain. Now, 

 in this same Catalogue, 53 acknowledged varieties are re- 

 corded, and these range over 7-7 provinces; whereas, the 

 species to which these varieties belong range over 14-3 

 provinces. So that the acknowledged varieties have 



