DEATH 277 



the same instincts and habits as its parent. 

 Difficulty is sometimes felt in accounting for such 

 instincts. The individual wasp, it is true, derives 

 no advantage whatever from its ingenuity ; but the 

 gain to the species is enormous ; and the preserva- 

 tion of the habit is due to the fact that those indi- 

 viduals which took the greatest care to make pro- 

 vision for their young would be most likely to give 

 rise to offspring which would survive in the struggle 

 for existence. Natural selection would tend to 

 preserve the instinct because it is advantageous to 

 the species, though of no benefit whatever to the 

 individual. 



So with regard to death; Weismann argues 

 that the origin thereof is to be found in the con- 

 sideration that it is advantageous to the species 

 that individuals should die. The argument is 

 perhaps best stated in his own words. "Let us 

 imagine," he says, " that one of the higher animals 

 became immortal ; it then becomes perfectly obvious 

 that it would cease to be of value to the species to 

 which it belonged. Suppose that such an immortal 

 individual could escape all fatal accidents through 

 infinite time, a supposition which is of course 

 hardly conceivable. The individual would never- 

 theless be unable to avoid from time to time slight 

 injuries to one or another part of its body. The 

 injured parts could not regain their former integrity, 

 and thus the longer the individual lived the more 

 defective and crippled it would become, and the less 

 perfectly would it fulfil the purpose of its species. 

 Individuals are injured by the operation of external 



