44 ON THE ORIGIN OF SPECIES 



are in several respects the most important for us. We 

 have every reason to believe that many of these 

 doubtful and closely-allied forms have permanently 

 retained their characters in their own country for a 

 long time ; for as long, as far as we know, as have 

 good and true species. Practically, when a naturalist 

 can unite two forms together by others having inter- 

 mediate characters, he treats the one as a variety of 

 the other, ranking the most common, but sometimes 

 the one first described, as the species, and the other as 

 the variety. But cases of great difficulty, which I will 

 not here enumerate, sometimes occur in deciding 

 whether or not to rank one form as a variety of 

 another, even when they are closely connected by 

 intermediate links ; nor will the commonly-assumed 

 hybrid nature of the intermediate links always remove 

 the difficulty. In very many cases, however, one form 

 is ranked as a variety of another, not because the 

 intermediate links have actually been found, but 

 because analogy leads the observer to suppose either 

 that they do now somewhere exist, or may formerly 

 have existed ; and here a wide door for the entry of 

 doubt and conjecture is opened. 



Hence, in determining whether a form should be 

 ranked as a species or a variety, the opinion of natural- 

 ists having sound judgment and wide experience seems 

 the only guide to follow. We must, however, in many 

 cases, decide by a majority of naturalists, for few well- 

 marked and well-known varieties can be named which 

 have not been ranked as species by at least some com- 

 petent judges. 



That varieties of this doubtful nature are far from 

 uncommon cannot be disputed. Compare the several 

 floras of Great Britain, of France, or of the United 

 States, drawn up by different botanists, and see what 

 a surprising number of forms have been ranked by one 

 botanist as good species, and by another as mere 

 varieties. Mr. H. C. Watson, to whom I lie under deep 

 obligation for assistance of all kinds, has marked for 

 me 182 British plants, which are generally considered 



