DAE WIN AND HIS CRITICS. 51 



will be convenient here also to sum it up in as 

 few explanatory words as possible, though some- 

 what more fully than in the passages just 

 quoted. 



The calculations of Malthus and subsequent 

 writers, show that all living organisms tend to 

 increase in a geometrical ratio ; and therefore, 

 any single species of animal or plant (however 

 small, or however slowly it might reproduce its 

 kind) if allowed to multiply unchecked, would 

 speedily overrun the earth. 



But instead of this being the case, the actual 

 number of individuals of any given species 

 existing at one time, remains almost stationary; 

 and hence the number of deaths must on an 

 average equal that of the births.* It therefore 

 follows that every species is exposed to adverse 

 influences which keep its numbers down to about 

 the average, and thus prevent any inordinate 

 increase. 



Every individual of a species resembles its 

 parents in most particulars, but is subject to an 

 indefinite number of slight modifications, which 



* Greg, in his essay, " Malthus Notwithstanding," argues that other 

 checks besides death may sometimes operate in preventing an undue 

 increase of population. See his "Enigmas of Life." 



E2 



