EFFECT OF SELECTION I41 
negative variation* from the proper type of the new 
variety. In this way the novelty may not appear to be 
very far removed from a high normal variation of the 
original type. The behaviour of the progeny of the two 
types, however—types which might thus in themselves 
be readily confused—is entirely different, and a ready 
means of distinguishing them is thereby provided. 
Each set of offspring shows regression to its own proper 
modal value ; so that the offspring of the novelty show 
a further marked development of the new features, 
whilst the offspring of an extreme normal variation 
resemble the type of the original form more closely 
than they do their own immediate progenitor. 
If new types are not produced among domesticated 
productions by the action of artificial selection, and all 
that selection can effect is to pick out definite novelties 
when they occur, the analogy between natural selec- 
tion and artificial selection breaks down, and a large 
and important section of the evidence in favour of the 
production of natural species by the action of natural 
selection is destroyed. In the place of this explana- 
tion de Vries would put the theory of mutation, ac- 
cording to which new species arise by single steps as 
definite novelties, just in the same way as we find that 
domestic varieties are produced. More than this, de 
Vries believes that he has discovered a set of new 
species in the very act of originating from an old 
one in this way, a discovery which affords the basis 
* I.e., a variant belonging to a class situated some dis- 
tance from the mode of normal variability of the novelty, 
and on the side of it nearest to the mode of the original type. 
