THE STRUGGLE FOR EXISTENCE. 143 



of field-mice, which destroy their combs and nests ; and 

 Colonel Newman, who has long attended to the habits 

 of humble-bees, believes that more than two-thirds of 

 them are thus destroyed all over England. Now, the 

 number of mice is largely dependent, as every one 

 knows, on the number of cats ; and Col. Newman says, 

 ' Near villages and small towns I have found the nests 

 of humble-bees more numerous than elsewhere, which I 

 attribute to the number of cats that destroy the mice. 

 Hence it is quite credible that the presence of a feline 

 animal in large numbers in a district might determine, 

 through the intervention first of mice and then of bees, 

 the frequency of certain flowers in that district' " 



The closer the kindred of the competitors, the more 

 ardent is the struggle for the existence ; for the more 

 adjacent organisms differ in their requirements, the less 

 do they interfere with one another, and the more will 

 each be able to exhaust the resources of the vicinity for 

 its own benefit. This seems to be flatly contradicted 

 by the great series of associated plants and animals ; 

 but on closer inspection they also form no exception to 

 the rule, as, often by their very number they render 

 existence possible and easy to one another, and increase 

 exactly in the degree permitted by the stock of nutri- 

 ment. If among associated plants or gregarious animals 

 a surplus production occurs, competition and conflict in- 

 stantly commence, and life is regulated in every respect 

 exactly as in species less remarkable for the number of 

 individuals. 



Our proposition that the vehemence of the struggle 

 rises with the closeness of the kindred, is thus univer- 

 sally valid. Such a rapid war of extermination is rarely 



