HEREDITY AND VARIATION. 31 



Variations and heredity are generally estimated, 

 not according to the inner nature of the mature 

 individuals, but according to their relation in suc- 

 cessive generations, since heredity is assumed when 

 the ontogenetic characters remain the same, and 

 variation when previously latent characters become 

 visible. But these phenomena belong to another 

 department of science; they concern the possibility 

 and reality of development of the idioplasmic deter- 

 minants. 



17. VARIETY, RACE, MODIFICATION. 



From the multifarious variations of organisms 

 proceed various categories of kinship. Varieties 

 arise by extremely slow changes in the idioplasm 

 due to the perfecting process and adaptation. Since 

 these are conditioned by the same causes, they fol- 

 low in all individuals of the same variety in uniform 

 manner. Varieties are uniform, entirely constant 

 under the most various external conditions, in gen- 

 eral cross only with difficulty with related varieties, 

 are not varied by accidental crosses, and persist 

 through geological periods. Varieties belong to 

 feral nature rather than to culture ; they can assume 

 all possible modifications without injury to their 

 specific characteristics, but can show no distinctions 

 of races, for all beginnings of race formation are 

 destroyed by free intercrossing. They differ from 

 species only in that they are to be designated as 

 more closely related species, or species as more 



