22 SOCIAL EVOLUTION 



stant from year to year. There seems to be no great 

 fluctuation in tlic number of any species from year to 

 year.-' Yet this apparently high death-rate of robins is 

 surpassed by tliat of many other species. Among many 

 fishes tlie "yearly death-rate is two hundred and fifty 

 thousand times as great as the i)ermanent population, 

 since on the average only one male and one female out 

 of the half million of young survive to take the place of 

 their parents and keep the number of individuals in the 

 species up to the usual mark." For every starfish living 

 nearly half a million die each year.^ Indeed, taking 

 organic nature as a whole probably not one in a thousand 

 young is allowed to survive to the age of reproduction.^ 



Adults Young 



One pair of adult robins 2 



First year, their young 4 



Second year 6 12 



Third year IS 36 



Fourth year 54 108 



Fifth year 162 324 



Sixth year 486 972 



Seventh year 1,458 2,916 



Eighth year 4,374 8,748 



Ninth year 13,122 26,244 



Tenth year 39,366 78,732 



End of tenth year 118,098 



End of twentieth year 20,913,948,846 



While this law applies to the lower forms of life, plants 

 and animals, one might say that men are not subject to 

 it. It is true that the rigors of the crude struggle have 

 been somewhat modified by man's greater cunning and 

 forethought, but the law holds for men just as it doea 



^ Ibid., pp. 14-15. * Romanes, op cil., p. 2G2. 



