234 



REPRODUCTION, PUBERTY AND LONGEVITY. 



Q) ^ ^ 



FIG. 11— APPROXIMATE AVERAGE AGES AT REPRODUCTION, ILLUSTRAT- 

 ING RELATIVE INTELLIGENCE. 



LENGTH OF TIME DEVELOPMENT CONTINUES. 



In the higher animals the degree of activity, both mental and 

 physical, necessary for continued development lasts to a very late 

 period in life. We may observe the increase in intelligence, coming 

 from increased age, as low in the scale as among fishes. Young 

 fish may be easily caught, but old fish are wary and are caught 

 with difficulty. That the physical powers persist, and even increase, 

 up to nearly the limit of life, we see principally exemplified in 

 polygamous animals, among which an old male is almost always 



