CHAPTER VI 
EXPERIMENTAL HYBRIDIZING 
WITHIN the limits of the Linnzan species it has been found 
that varieties, or races, or breeds, are generally perfectly fertile 
when crossed, and in recent years these fertile crosses have 
been much studied. In some cases it has been found that a 
character that is different in two parents blends in the offspring, 
and may or may not separate again; in other cases, however, 
a character that differs in the parents does not blend, and all the 
offspring of the first generation are like one of the parents. The 
inheritance is alternate. If hybrids of this kind are bred to 
each other, the original character of one of the grandparents 
may reappear in some of the offspring, the contrasting char- 
acter of the other grandparent in others. These cases follow 
what is known as Mendel’s law. 
It is sometimes stated that Mendel’s law applies only to 
crosses between varieties, and this is true for many cases; but 
characters that are entirely new to the race may also follow 
Mendel’s law; and if the appearance of one new character suf- 
fices to characterize a new form as an elementary species, we 
must conclude that the characters of some elementary species 
also follow Mendel’s law of alternate inheritance. 
Mendel’s Law 
In 1865 Mendel published the results of an elaborate series 
of experiments that he had made with varieties of peas. It is 
strange that so important a discovery should have been entirely 
neglected for thirty-five years, especially since the question of 
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