Essays on Life 



one hand, why the age of puberty marks the 

 beginning of completed development a riddle 

 hitherto not only unexplained but, so far as 

 I have seen, unasked ; it explains, on the other 

 hand, the phenomena of old age hitherto 

 without even attempt at explanation. 



Sixthly, those organisms that are the longest 

 in reaching maturity should on the average 

 be the longest-lived, for they will have re- 

 ceived the most momentous impulse from the 

 weight of memory behind them. This har- 

 monises with the latest opinion as to the facts. 

 In his article on Weismann in the Contempo- 

 rary Review for May 1890, Mr. Romanes 

 writes : " Professor Weismann has shown that 

 there is throughout the metazoa a general corre- 

 lation between the natural lifetime of indi- 

 viduals composing any given species, and the 

 age at which they reach maturity or first be- 

 come capable of procreation." This, I believe, 

 has been the conclusion generally arrived at 

 by biologists for some years past. 



Lateness, then, in the average age of repro- 

 duction appears to be the principle underlying 

 longevity. There does not appear at first 



sight to be much connection between such 



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