INTRODUCTORY 21 



failure of the other on the one hand, and the specific character* 

 istics which distinguish the two forms on the other. The or- 

 thodox Selectionist would, as usual, appeal to ignorance. We 

 ask what can vespertina gain by its white flowers, its more lan- 

 ceolate leaves, its grey seeds, its almost erect capsule-teeth, 

 its longer fruits, which diurna loses by reason of its red flowers, 

 more ovate leaves, dark seeds, capsule-teeth rolled back, and 

 shorter fruits? We are told that each of these things may 

 affect the viability of their possessors. We cannot assert that 

 this is untrue, but we should like to have evidence that it is true. 

 The same problem confronts us in thousands upon thousands 

 of examples, and as time goes on we begin to feel that speculative 

 appeals to ignorance, though dialectically admissible, provide 

 an insufficient basis for a proposition which, if granted, is to 

 become the foundation of a vast scheme of positive construction. 



One thing must be abundantly clear to all, that to treat two 

 forms so profoundly different as one, because intermediates of 

 unknown nature can be shown to exist between them, is a mere 

 shirking of the difficulties, and this course indeed creates artificial 

 obstacles in the way of those who are seeking to discover the 

 origin of organic diversity. 



In the enthusiasm with which evolutionary ideas were re- 

 ceived the specificity of living things was almost forgotten. 

 The exactitude with which the members of a species so often 

 conform in the diagnostic, specific features passed out of account ; 

 and the scientific world by dwelling with a constant emphasis 

 on the fact of variability, persuaded itself readily that spe- 

 cies had after all been a mere figment of the human mind. 

 Without presuming to declare what future research only can 

 reveal, I anticipate that, when variation has been properly 

 examined and the several kinds of variability have been suc- 

 cessfully distinguished according to their respective natures, 

 the result will render the natural definiteness of species increas- 

 ingly apparent. Formerly in such a case as that of the two 

 Lychnis species, the series of "intermediates" was taken to be a 

 palpable proof that vespertina "graded" to diurna. It is this 

 fact, doubtless, upon which Bentham would have relied in sug- 



