84 THE EVOLUTION OF LIVING BEINGS. 



Every child will tell you : wild rabbits are grey, but 

 people better acquainted with rabbits, gamekeepers 

 f. i., know that occasionally black and orange-yellow 

 rabbits occur in nature. As these are evidently much 

 in the minority compared with the grey ones, they 

 jump to the conclusion that the grey ones aretheorig- 

 nal form, while the black and the yellow ones are the 

 varieties derived from this original form. 



Systematists use to express this by saying that the 

 most common form is the ,,species", while the rare ones 

 are varieties". 



Now the cause of this conception really is nothing 

 but the overwhelming majority of the greys. 



If l / 3 of all wild rabbits were grey, x / 3 yellow and Vs 

 black, one would probably have made 3 species of them, 

 and never have entertained the idea of variability or, 

 if yet some systematist had united them to one species, 

 one would anyhow, if the idea of a common descent 

 had cropped up, been at a perfect loss to decide which 

 form was the original one : the grey, the black or the 

 yellow one, which had to be considered to be derived. 



So that, if it was not exclusively the fact that within 

 most Linnean species, especially within animal ones, 

 one form is in the overwhelming majority which cau- 

 sed the conception of variability, it certainly was this 

 fact which led to the conception of a single form being 

 the ancestor of all others. 



Now as we calculated already, there is no reason what- 

 ever for such a contention. 



By crossing the type in the majority with those in 

 the minority, we find that the type in the majority is 



