46 INHERITANCE, VARIATION AND SELECTION. 



As fixity of character is in contradistinction to variability, in a 

 cross between two races, that race will be prepotent which has been 

 the less variable during the immediately preceding generations. 

 The white race is more variable than the negro, and in crosses 

 between them we find negro characteristics predominate. It is well 

 known that animals and plants under domestication are more vari- 

 able than they are in the wild state, and it is also known that this 

 variability is induced by the stimulated conditions existing through 

 successive generations. As civilization, as we know it, is a series of 

 intensely stimulated conditions, we see why the civilized races are 

 more variable and less prepotent than uncivilized races. This 

 generalization must, however, be used with caution because the 

 very intensity of civilization acts to give a fixity to some character- 

 istics which are less firmly fixed by a less degree of intensity. 



GROWTH AND REPAIR. 



Growth is essentially a slow process, depending upon the amount 

 of material digested and assimilated over and above what is neces- 

 sary to maintain the individual in a uniform condition. As this 

 surplus is always a limited quantity, any acceleration of growth in 

 one part is accompanied by a lack of growth or degeneracy in some 

 other part. Strength and endurance, in the sense of vitality, are 

 as much matters of growth as is mere increase in bulk, and the 

 development of these qualities absorbs assimilated nutriment just as 

 completely. Those animals and plants which are strong, enduring 

 and tenacious of life are those which grow slowly in bulk, while 

 those which increase rapidly in size are weak and are easily killed. 

 Functional power is also a matter of slow development, and while 

 it is associated with the size of the functioning organ it is not pro- 

 portional to such size. It also absorbs nourishment in its develop- 



