DIVISION OF LABOUR. 27 T 
great number of weeds can exist, and, moreover, in places 
which could not have been occupied by corn-plants. ‘ The 
more dry and sterile places of the ground, in which no corn- 
plant would thrive, may still furnish sustenance to weeds of 
different kinds ; and such species and individuals of weeds 
will more readily be able to exist in such conditions, in pro- 
portion as they are suited to adapt themselves to the dif- 
ferent parts of the ground. It is the same with animals. It 
is evident that a much greater number of animal indivi- 
duals can live together in one and the same limited district, if 
they are of various and different natures, than if they 
are all alike. There are trees (for example, the oak) on 
which a couple of hundred of different species of insects live 
together. Some feed on the fruits of the tree, others on the 
leaves, others again on the bark, the root, ete. It would be 
quite impossible for an equal number of individuals to live 
on this tree if all were of one species; if, for example, all fed 
on the bark, or only upon the leaves. Exactly the same is 
the case in human society. In one and the same small town, 
only a certain number of workmen can exist, even when 
they follow different occupations. The division of labour, 
which is of the greatest use to the whole community, as well 
as to the individual workman, is a direct consequence of the 
struggle for life, of natural selection; for this struggle can 
be sustained more easily the more the activities, and hence, 
also, the forms of the different individuals deviate from 
one-another. The different function naturally produces its 
reaction in changing the form, and the physiological divi- 
sion of labour necessarily determines the morphological 
differentiation, that is, the “divergence of character.” *7 
Now, I beg the reader again to remember that all species 
