THE LAWS OP VARIABILITY. 77 



C. Watson, to whom I lie under deep obligation for as- 

 sistance of all kinds, has marked for me one hundred and 

 eighty-two British plants, which are generally considered 

 as Tarieties, but which have all been ranked by botanists 

 as species ; and in making this list he has omitted many 

 trifling varieties, but which nevertheless have been ranked 

 by some botanists as species, and he has entirely omitted 

 several highly polymorphic genera. Under genera, in- 

 cluding the most polymorphic forms, Mr. Babington gives 

 two hundred and fifty-one species, whereas Mr. Bentham 

 gives only one hundred and twelve — a difference of one 

 hundred and thirty-nine doubtful forms ! 



SPECIES AK AEBITEAET TEEM. 



Certainly no clear line of demarkation has 

 *°* ■ as yet been drawn between species and sub- 

 species — that is, the forms which in the opinion of some 

 naturalists come very near to, but do not quite arrive at, 

 the rank of species ; or, again, between sub-species and 

 well-marked varieties, or between lesser varieties and in- 

 dividual differences. These differences blend into each 

 other by an insensible series ; and a series impresses the 

 mind with the idea of an actual passage. 



Hence I look at individual differences, though of 

 small interest to the systematist, as of the highest impor- 

 tance for us, as being the first steps toward such slight 

 varieties as are barely thought worth recording in works 

 on natural history. And I look at varieties which are in 

 any degree more distinct and permanent as steps toward 

 more strongly-marked and permanent varieties ; and at 

 the latter, as leading to sub-species, and then to species. 

 The passage from one stage of difference to another may, 

 in many cases, be the simple result of the nature of the 



