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 eloser 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 
asurplus 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 
