ANIMALS MADE USEFUL 19 
i. ¢., tall or short, with rounded seeds or wrinkled, with 
yellow cotyledons or green cotyledons. 
Varieties differing in stature were used: One a giant of 6 to 7 
feet high, the other a dwarf 9 inches to 18 inches high. “These were 
crossed, and the resulting seeds grew into plants which were all 
tall. The character of tallness which appeared in this cross-bred 
generation to the exclusion of dwarfness was called by Mende! the 
dominant character, the other recessive. The tall cross-bred peas were 
left to self-fertilize, and in their progeny there were talls and 
dwarfs, in the average proportions of 3:1. When the dwarfs of this 
generation were allowed to self-fertilize, their offspring were ail 
dwarfs, and further generations bred from them were also dwarfs. 
In other words, one-fourth of the generation were quite pure as re- 
gards dwarfness, and these were called pure recessives. But when 
the talls of the second generation were left to self-fertilize, their 
offspring were of two kinds: (a) plants which produced talls and 
dwarfs in the 3:1 proportion, and (b) similar plants which pro- 
duced talls only, being pure as regards tallness. These “impure 
dominants” and “pure dominants” occur in the ratio of 2 to 1. Thus 
the second generation, resulting from the self-fertilization of the 
cross-bred forms or hybrids, consists of 25 per cent pure dominants, 
50 per cent impure dominants, and 25 per cent pure recessives.” 
12. Dominant and recessive characters.——Important 
conclusions in a fundamental way have been reached as 
the result of what is now known as Mendel’s law. This 
law applies to certain kinds of hybridization. A hybrid, 
you know, is the resulting offspring when two plants or 
two animals of different varieties or breeds have been 
mated or bred. In such crossings it is supposed that the 
generative cells, or gametes, produced by cross-breds are 
of two kinds, each kind bearing only one of two con- 
trasted or alternative characters which do not blend. 
These characters are known as dominant and recessive. 
“The idea may be better understood by using mice as an illus- 
tration. When what are called waltzing mice are crossed with 
normal mice, in the hybrid waltzing is recessive, the normal is dom- 
inant. When the members of this generation are in-bred, their 
progeny consists of normal mice and waltzing mice in the propor- 
tion 3:1. The recessive waltzers of this generation are quite pure 
as regards waltzing, and will produce only waltzers for as many 
generations as one likes to breed them. But the dominants of the 
same generation turn out to be two kinds (though they appear to 
