INTRODUCTORY 11 



systematists of all countries in the several groups, but with 

 rare exceptions they show little misgiving as to the fundamental 

 reality of specific differences. That the systematists consider 

 the species-unit as of primary importance is shown by the 

 fact that the whole business of collection and distribution of 

 specimens is arranged with regard to it. 



Almost always the collections are arranged in such a way that 

 the phenomena of variation are masked. Forms intermediate 

 between two species are, if possible, sorted into separate boxes 

 under a third specific name. If a species is liable to be constantly 

 associated with a mutational form, the mutants are picked out, 

 regardless of the circumstances of their origin, from the samples 

 among which they were captured, and put apart under a special 

 name. Only by a minute study of the original labels of the 

 specimens and by redistributing them according to locality and 

 dates, can their natural relations be traced. The published 

 accounts of these collections often take no notice of variations, 

 others make them the subject of casual reference. Very few 

 indeed treat them as of much importance. From such indi- 

 cations it is surely evident that the systematists attach to the 

 conception of species a significance altogether different from that 

 which Darwin contemplated. 



I am well aware that some very eminent systematists regard 

 the whole problem as solved. They hold as Darwin did that 

 specific diversity has no physiological foundation or causation 

 apart from fitness, and that species are impermanent groups, 

 the delimitations of which are ultimately determined by en- 

 vironmental exigency or "fitness." The specific diversity of 

 living things is thus regarded as being something quite different 

 in nature from the specific diversity of inorganic substances. 

 In practice those who share these opinions are, as might be an- 

 ticipated, to be found among the 'lumpers' rather than among 

 the 'splitters.' In their work, certainly, the Darwinian theory 

 is actually followed as a guiding principle; unanalysed inter- 

 gradations of all kinds are accepted as impugning the integrity 

 of species; the underlying physiological problem is forgotten, 

 and while the product is amost valueless as a contribution to 



