EFFECTS OF SEXUAL REPRODUCTION. 253 



dition corresponding to the condition of its parents at the time of 

 conception. This initial velocity is accelerated or retarded by each 

 individual according as his functional activity is greater or less 

 than that of his immediately preceding ancestors. 



TIME OF APPEARANCE OF CHARACTERS VARIED BY AGE AT WHICH 



REPRODUCTION OCCURS. 



Applying this to the brain of man and assuming that the func- 

 tional activity be uniform from generation to generation, then, if 

 the average age of reproduction coincided with the normal age of 

 maturity (which may be assumed to be about 30 years for man), 

 the race would neither advance nor recede, but remain stationary. 

 If, in a particular instance, the age of reproduction for a healthy 

 individual be advanced from 30 to 50, and this advance in age be 

 accompanied by a functional activity sufficient to cause this indi- 

 vidual's brain at the age of 50 to be of greater functional capacity 

 than it was at the age of 30, then the offspring, following the same 

 grade of activity that its parent followed, would, at the age of 30, 

 have a functional capacity approximately equal to that its parent 

 had at the age of 50. If the act of reproduction occurs when the 

 parent is 15 instead of 50, then the rate of development of the 

 offspring would be slower and, at the age of 30, he would be devel- 

 oped only about as far as his parent was at the age of 15. What 

 the offspring is at the age of maturity, therefore, depends upon the 

 amount the parent has developed at the time of conception. The 

 amount of this development depends, of course, upon the degree 

 of functional activity and the length of time the functional activity 

 is continued. As the parent is itself an offspring and is in like 

 measure dependent upon its parents, it is evident that each person's 

 inheritance is the product of the average ancestral activity and the 

 average length of time this activity continued for each ancestor. 



