( Ixxviii ) 



down in the clear, calm, and simple language Which did sd 

 much to convince an unwilling v/orld. 



Darwin is speaking of the revolution which the acceptance 

 of his views will bring about. " Systematists will be able to 

 pursue their labours as at present ; but they will not be 

 incessantly haunted by the shadowy doubt whether this or 

 that form be in essence a species. This, I feel sure, and I 

 speak after experience, will be no slight relief. The endless 

 disputes whether or not some fifty species of British brambles 

 are true species will cease. /Systematists will have only to 

 decide [not that this will he easy) lohether any form he siiffici- 

 ently constant and distinct from other forms to he capahle of 

 definition, and if definable, whether the differences he sufiiciently 

 important to deserve a specific name. This latter point will 

 become a far more essential consideration than it is at present; 

 for differences, however slight, between any two forms, if not 

 blended by intermediate gradations, are looked at by most 

 naturalists as sufficient to raise both forms to the rank of 

 species. Hereafter we shall he compelled to acknovjledge that 

 the only distinction hetween sjyecies and ivell-marhed varieties is, 

 that the latter are known, or helieved, to he connected at the 

 j/resent day hij intermediate gradations, whereas species v)ere 

 formerly thus connected. Hence, without quite rejecting the 

 consideration of the present existence of intermediate grada- 

 tions between any two forms, we shall be led to weigh more 

 carefully, and to value higher, the actual amount of difference 

 between them. It is quite possible that forms now generally 

 acknowledged to be merely varieties may hereafter be thought 

 worthy of specifie names, as with the primrose and cowslip ; 

 and in this case scientitic and common language will come 

 into accordance. In short, we shall have to treat species in 

 the same manner as those naturalists treat genera, who admit 

 that genera are merely artificial combinations made for con- 

 venience. This may not be a cheering prospect, but we shall 

 at least be freed from the vain search for the undiscovered 

 and undiscoverable essence of the term species." I have 

 quoted from pages 484, 485 of the original edition (1859), 

 and have italicised the sentences in which Darwin defines a 

 species and distinguishes it from a variety. 



