54 ON THE ORIGIN OF SPECIES 



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 acknow- 

 ledged varieties are recorded, and these range over 7*7 

 provinces ; whereas, the species to which these varieties 

 belong range over 14*3 provinces. So that the acknow- 

 ledged varieties have very nearly the same restricted 

 average range, as have those very closely allied forms, 

 marked for me by Mr. Watson as doubtful species, but 

 which are almost universally ranked by British botanists 

 as good and true species. 



Finally, then, varieties have the same general 

 characters as species, for they cannot be distinguished 

 from species, — except, firstly, by the discovery of 

 intermediate linking forms, and the occurrence of 

 such links cannot affect the actual characters of the 

 forms which they connect; and except, secondly, by a 

 certain amount of difference, for two forms, if differing 

 very little, are generally ranked as varieties, notwith- 

 standing that intermediate linking forms have not been 

 discovered ; but the amount of difference considered 

 necessary to give to two forms the rank of species is 

 quite indefinite. In genera having more than the 

 average number of species in any country, the species 

 of these genera have more than the average number of 

 varieties. In large genera the species are apt to be 

 closely, but unequally allied together, forming little 

 clusters round certain species. Species very closely 

 allied to other species apparently have restricted 

 ranges. In all these several respects the species of 

 large genera present a strong analogy with varieties. 

 And we can clearly understand these analogies, if 

 species have once existed as varieties, and have thus 

 originated : whereas, these analogies are utterly in- 

 explicable if each species has been independently 

 created. 



We have, also, seen that it is the most flourishing 



