26O MENTAL AND PHYSICAL RESULTS. 



Darwin uses these animals for the greater number of his illustrations 

 of sexual selection. These phenomena are explainable only on the 

 theory of use-inheritance, and are simply other illustrations of the 

 previously demonstrated fact that the offspring tend to be repro- 

 ductions of the parents as they existed at the time of conception, 

 and not as they existed at some previous time or will exist at some 

 future time. 



RELATION OF MENTAL POWER TO MENTAL APTITUDE. 



It has been shown that mental power is the product of a series 

 of slowly moving generations, and that mental aptitude is the 

 product of a single generation, the quality of which is determined 

 to a considerable extent by the age at which reproduction takes 

 place. Age, however, is not the controlling factor in mental apti- 

 tudes, but an approximate method of determining the condition 

 of the parent at the time of conception. Whatever has been in- 

 tensely interesting to the parents during a few years immediately 

 preceding the conception and has influenced their actions and molded 

 their characters, will be transmitted to the offspring and will mold 

 his character to a large extent throughout life. As different things 

 influence the same parent in different degrees at different periods 

 of life, the actual influence transmitted to a child is often lost sight 

 of when he is measured in the light of influences existing at some 

 later period in the life of the parent. A man who has become 

 famous as a statesman or a mathematician may have been, at an 

 earlier period in his life, an enthusiast over art or literature. A 

 son conceived at this earlier period exhibits an inclination toward 

 these pursuits, and the world, not knowing these earlier influences, 

 wonders because the son does not inherit those traits which made 

 the father famous. 



