158 Controversial Questions. 



term ; but our knowledge of the mode of the origin of 

 species will not help us in this investigation.^ The study 

 of variability, in plants and animals, as well as in the 

 physical characters of man may thus serve a higher pur- 

 ix)se. 



It is singularly fortunate, in the present state of 

 affairs, that these analogies should be limited to varia- 

 bility as opposed to mutability. Variability is accessible 

 to investigation from many points of view, which is far 

 from being the case with mutability. Many principles 

 in variability have been discovered and dealt with by 

 OuETELET and Galton and their followers : the methods 

 of this school can be partly applied directly to the in- 

 vestigation of mental characters and partly effect a con- 

 siderable simplification of treatment. 



There lies here a wide and fertile field of investiga- 

 tion, especially for botanists.- One of the most impor- 

 tant conditions in experiments on selection is the num- 

 ber of individuals in each generation ; and plants readily 

 lend themselves to cultivation by hundreds without any 

 of the ill effects which usually attend overcrowding. Such 

 experiments are Avell-nigh impossible in the case of ani- 

 mals : and out of the question in the case of man. Here, 

 as in many other spheres, the botanist must take the lead 

 and the zoologist and anthropologist will follow after- 

 wards. 



Of late years the statistical study of variability has 

 become specialized as a distinct branch of science thanks 

 to the labors of Bateson and Weldon among zoologists, 

 LuDWiG among botanists and Karl Pearson and Dunc- 



^ See also H. J. Haycraft, Darivinism and Race Progress, and 

 further, on the possibility of replacing selection by improved nutri- 

 tion : L'Unite dans la Variation, p. 21. 



' L' Unite dans la Variation, loc. cit., pp. 14-15. 



