396 STUDIES, SCIENTIFIC AND SOCIAL chap. 



variation in some individuals of exceptional vigour, it may 

 increase by interbreeding, and its repeated production 

 being perhaps favoured by some local conditions, it may 

 come to form a marked local variety. Now, if the conditions 

 become unfavourable to the species in the area occupied 

 by the type, this may in course of time become extinct, 

 and the variety distinguished by the altogether useless 

 character will remain as the only representative of the 

 species. It may be admitted that such a mode of origin 

 of a non-utilitarian specific character is conceivable, but 

 whether it ever actually occurs in nature may be doubted ; 

 while if it does occur, it must be owing to so rare a com- 

 bination of circumstances that it can produce no such 

 general prevalence of useless specific characters as is 

 claimed by the advocates of that theory.^ 



In order to ascertain whether the immediate antecedent 

 to such a mode of species-formation as is suggested is at 

 all common, and thinking that British flowering plants 

 offer the best materials for its detection, I put the case to 

 two experienced British botanists as follows : — Are there 

 any examples within your knowledge of well-marked 

 varieties (not mere individual states due to local conditions) 

 which occupy a considerable area to the exclusion of the 

 parent species, and which do not occupy any area, or only 

 a very small one, with the type ? Each of them suggested 

 several species which seemed to answer to the conditions, 

 but on further consideration it appeared that they did not 

 do so, and we were finally reduced to a single case, that 

 of one of the species of Rubus, a genus which most 

 botanists will regard as a very unsafe one to draw any 

 conclusions from. Ruhus radula, Weihe, is said to be 

 abundant in the Midland parts of England, but in the 

 Southern and South-western counties to be replaced by 

 the variety anglicanus of W. M. Rogers, the type never 

 having been found in the area occupied by this variety. 

 If this is the case, and the two forms, said to be easily 

 recognizable, really occupy distinct areas and nowhere 



^ If, however, the variation is preserved because it occurs in 

 exceptionally vigorous individuals, it is correlated with a character 

 which is useful. 



