156 ‘THE HISTORY OF CREATION. 
propagation and nutrition. These two fundamental quali- 
ties are transmissivity, or the capability of transmitting by 
inheritance, and mutability, or the capability of adaptation. 
The breeder starts from the fact that all the individuals of 
one and the same species are different, though in a very 
slight degree, a fact which is as true of organisms in a wild 
as in a cultivated state. If you look about you in a forest 
consisting of only a single species of tree, for example of 
beech, you will certainly not find in the whole forest two 
trees of this kind which are absolutely identical or perfectly 
equal in the form of their branches, the number of their 
branches and leaves, blossoms and fruits. Special differences 
occur everywhere, just as in the case of men. There are 
no two men who are absolutely identical, perfectly equal in 
size, in the formation of their faces, the number of their 
hairs, their temperament, character, etc. The very same is 
true of individuals of all the different species of animals and 
plants. It is true that in most organisms the differences are 
very trifling to the eye of the uninitiated. Everything 
here essentially depends on the exercise of the faculty of 
-discovering these often very minute differences of form. The 
shepherd, for example, knows every individual of his flock, 
solely by accurately observing their features, while the 
uninitiated are incapable of distinguishing at all the different 
individuals of one and the same flock. This fact of the 
individual difference is the extremely important foundation 
on which the whole of man’s power of breeding rests. If 
individual differences did not exist everywhere, man would 
not be able to produce a number of different varieties or 
races from one and the same original stock, We must, at 
the outset, hold fast the principle that the phenomenon is 
