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 difierences 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 difierences of form. The 

 shepherd, for example, knows every individual of his fiock, 

 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 



