372 THE HISTORY OF CREATION. 
only in the simplest non-sexual manner. Even now all 
Protista, as well as all the countless forms of cells, which 
constitute the body of higher organisms, multiply themselves 
only by non-sexual generation. And yet there arise here 
“new species” by differentiation in consequence of natural 
selection. 
But even if we were to take into consideration the animal 
and vegetable species with separate sexes, in this case too 
we should have to oppose Wagner’s chief proposition, that 
“the migration of organisms and their formation of colonies 
is the necessary condition of natural selection.” August 
Weismann, in his treatise on the “Influence of Isolation 
upon the Formation of Species,” * has already sufficiently 
refuted that proposition, and has shown that even in one 
and the same district one bi-sexual species may divide itself 
into several species by natural selection. In relation to this 
question, I must again call to mind the great influence 
which division of labour, or differentiation, possesses, being 
one of the necessary results of natural selection. All 
the different kinds of cells constituting the body of the 
higher organisms, the nerve cells, muscle cells, gland cells, 
ete., all these “good species,” these “bonze species” of 
elementary organisms, have arisen solely by division of 
labour, in consequence of natural selection, although they 
not only never were locally isolated, but ever since their 
origin have always existed in the closest local relations one 
with another. Now, the same reasoning that applies to these 
elementary organisms, or “ individuals of the first order,” 
applies also to the many-celled organisms of a higher order 
which only ata later date have arisen as “good species” 
from among their fellows. 
