Acquired Characters and Effects of Nutrition. 131 



taking ''acquired characters" into consideration in the 

 whole domain of comparative biology and the theory of 

 descent. 



The study of these characters falls within the prov- 

 ince of variability in the restricted sense — in that of indi- 

 vidual or fluctuating variability. It lies within the limits 

 of the species themselves even when these limits are so 

 narrow that they serve merely to separate the elementary 

 species from one another. 



But within these limits there is heredity.^ The family 

 character, the improved races of the breeder and the few 

 scientific experiments in selection that exist prove this 

 up to the hilt. 



Are these variations brought about by external or 

 internal causes? Ploetz says, ''the causes must of course 

 be sought ultimately in external influences."- The bio- 

 metrician finds it simpler to suppose that it is indepen- 

 dent of the environment and is not causally connected 

 with any alteration in the external conditions of life.'"^ 

 But such an assumption is obviously only a preliminary 

 step, made only to insure simplicity in the treatment of 

 the phenomena investigated. 



There is much evidence to show that individual vari- 

 ations are occasioned by external influences. And if this 

 is so we should be justified in regarding individual vari- 

 ations as acquired qualities. For most authors call those 



^ We are not taking here into consideration the question of the 

 inheritance of the effects of wounds and mutilations. They are in- 

 herited perhaps exclusively when follozved by disease as Darwin 

 said (Variation, II, p. 57), that is by infection. 



^Alfred Ploetz, Die Tiichtigkeit unserer Rasse und der Schuta 

 der Schzvachcn, 1895, p. 2)^. See also p. 22,. Also Intracellularc Pan- 

 genesis, p. 29. 



^ G. DuNCKER. Die Mefhodc der Variationsstatistik. Roux's Ar- 

 chiv f. Entivick. Mech. d. Org., Vol. VIII, i, p. 115, (1899). 



