Psychophysical Variations 33 



researches already carried out by statistical methods, aim- 

 ing to determine the actual facts as to whether variations 

 have an intrinsic drift in certain directions, or whether the 

 appearance of such a drift is entirely due to processes of 

 selection within or without the organism. The newer view, 

 which holds that species originate in abrupt or ' sport ' 

 variation, called ' mutation,' strikes at the very founda- 

 tions of the Darwinian conception that is, if mutation 

 be considered not merely an exceptional case but the 

 normal mode of the origin of species. 1 We may accord- 

 ingly go a little more fully into the requirements of a 

 theory of determination. 



1 The appearance of the new journal, Biometrica, is witness to the vitality of 

 the movement to treat biological phenomena, notably variations, by exact 

 statistical and mathematical methods. Cf. the summary articles by Davenport 

 and Weldon on ' Variation,' and those on 'Natural Selection' and ' Muta- 

 tion ' by Poulton, in the Diet, of Philos. and Psychol. On mutation see 

 De Vries, Die Mutations tkeorie (1901). A summary article by De Vries 

 is to be seen in Science, May 9, 1902. It seems to the present writer a very 

 long step from the observation of single cases, admittedly very rare, of the 

 persistance of abrupt variations, to the theory of the ' Origin of Species by 

 Mutation.' For an able negative criticism of De Vries' work, written from 

 the point of view of recent statistical ' biometric ' researches, see Weldon, in 

 Biometrica, Vol. I. Part 3, pp. 365 ff. 



