258 MULTIPLE FACTORS 
effect on subsequent generations. Exactly the 
opposite results are expected when the population 
is heteroenegous for multiple factors at the beginning 
(see Fig. 62). In the latter case, selection of the 
mixed material will lead to the isolation of definite 
Fie. 62.—I. Five pure lines of beans (A, B, C, D, EF), and the popula- 
tion (A-E) that results when they are mixed. II. The upper figure repre- 
sents the original biotype, and the two figures below this, the two new 
biotypes that arose from it. (After Johannsen.) 
types and even to the produgtion of new types 
through recombination. This is the source of most 
of the success of the practical breeder. 
To what has been said, however, one additional 
consideration must be urged. Mutations may occur 
