I.] THE DURATION OF LIFE. 25 



hypothetically immortal individual would be shortened by the 

 amount which was useless to the species. It would be reduced 

 to a length which would afford the most favourable conditions 

 for the existence of as large a number as possible of vigorous 

 individuals, at the same time. 



If by these considerations death is shown to be a beneficial 

 occurrence, it by no means follows that it is to be solely ac- 

 counted for on grounds of utility. Death might also depend 

 upon causes which lie in the nature of life itself. The floating 

 of ice upon water seems to us to be a useful arrangement, 

 although the fact that it does float depends upon its molecular 

 structure and not upon the fact that its doing so is of any 

 advantage to us. In hke manner the necessity of death has 

 been hitherto explained as due to causes which are inherent in 

 organic nature, and not to the fact that it may be advantageous. 



I do not however beheve in the validity of this explanation ; 

 I consider that death is not a primary necessity, but that it has 

 been secondarily acquired as an adaptation. I believe that life 

 is endowed with a fixed duration, not because it is contrary to 

 its nature to be unlimited, but because the unlimited existence 

 of individuals would be a luxury without any corresponding 

 advantage. The above-mentioned hypothesis upon the origin 

 and necessity of death leads me to believe that the organism 

 did not finally cease to renew the worn-out cell material because 

 the nature of the cells did not permit them to multiply indefi- 

 nitely, but because the power of multiplying indefinitely was 

 lost when it ceased to be of use. 



I consider that this view, if not exactly proved, can at any 

 rate be rendered extremely probable. 



It is useless to object that man (or any of the higher animals) 

 dies from the physical necessity of his nature, just as the specific 

 gravity of ice results from its physical nature. I am quite ready 

 to admit that this is the case. John Hunter, supported by his 

 experiments on anabiosis, hoped to prolong the life of man in- 

 definitely by alternate freezing and thawing ; and the Veronese 

 Colonel Aless. Guaguino made his contemporaries believe that 

 a race of men existed in Russia, of which the individuals died 

 regularly every year on the 27th of November, and returned to 

 life on the 24th of the following April. There cannot however 

 be the least doubt, that the higher organisms, as they are now 



