BREEDING 111 



heredity implies not so much the transmission of con- 

 ditions as of tendencies. Speaking loosely, we often 

 say that consumption, insanity, and heart disease are 

 hereditary. Strictly speaking, the statement is never 

 true ; an inherent weakness, or susceptibility of lungs, 

 brain, or heart, a tendency of these organs, may be 

 transmitted, but not the diseases themselves. And so of 

 other conditions. The word " tendencies " is our " open 

 sesame." Two parents having qualities unlike, and often 

 mutually exclusive, cannot transmit these qualities to 

 their common offspring ; but they can transmit all their 

 tendencies to that offspring, even though these 

 tendencies be antagonistic. An organism cannot be 

 two things at once, but it may tend to be many 

 different things, antagonistic tendencies within it 

 constantly struggling for the mastery. Aided by 

 external conditions, the tendency at one time sub- 

 ordinate may at another time become dominant. 

 Failing of such favourable conditions, tendencies may 

 keep up an unequal and seemingly inefficient struggle 

 throughout the lifetime of an individual, without once 

 making themselves manifest, and yet be transmitted to 

 the offspring with such potential force as there to 

 become operative. . . . 



' A tendency may remain dormant and perhaps un- 

 suspected, not merely for one, but sometimes for many 

 generations, becoming at last manifest again, in a re- 

 mote descendant. And this is as true of mental and 

 moral tendencies as of physical. In short, the observed 

 facts would seem to warrant the conclusion that the 

 organism never relinquishes any tendency it has once 

 acquired, but holds it in stock, if need be, generation 



