CONCLUDING REMARKS 249 



tion or in community with their co-derivatives, have as a fact 

 arisen, which now pass in the lists of systematists as species. For 

 an excellent account of typical illustrations I would refer the 

 reader to the book lately published by R. E. Lloyd 14 on the rat- 

 population of India. The observations there recorded are typical 

 of the state of things disclosed whenever the variations of large 

 numbers of individuals are closely investigated, whether in 

 domestication or in natural conditions. 



Guided by such clues we may get a good way into the prob- 

 lem. We see the origin of colourable species in abundance. 

 Then, however, doubt arises whether though these new forms 

 are as good species as many which are accepted as such by even 

 cautious systematists, there may not be a stricter physiological 

 sense in which the term species can be consistently used, which 

 would exclude the whole mass of these petites esp&ces. 



If further we find that we have, with certain somewhat 

 doubtful exceptions, never seen the contemporary origin of a 

 dominant factor, or of inter-racial sterility between indubitable 

 co-derivatives, it needs no elaboration of argument to show that 

 the root of the matter has not been reached. 



Examination of the inter-relations of unquestionably distinct 

 species nearly allied, such as the two common species of Lychnis, 

 leads to the same disquieting conclusion, and the best suggestion 

 we can make as to their origin is that conceivably they may have 

 arisen as two re-combinations of factors brought together by the 

 crossing of parent species, one or both of which must be supposed 

 to be lost. 



All this is, as need hardly be said, an unsatisfying conclusion. 

 To those permanently engaged in systematics it may well bring 

 despair. The best course for them is once for all to recognise 

 that whether or no specific distinction may prove hereafter to 

 have any actual physiological meaning, it is impossible for the 

 systematist with the means at his disposal to form a judgment of 

 value in any given case. Their business is purely that of the 

 cataloguer, and beyond that they cannot go. They will serve 

 science best by giving names freely and by describing everything 



14 Lloyd, R. E., The Growth of Croups in the Animal Kingdom, London, 1912. 



