How Darwinism Stands To-Day 383 



is dominant over the recessive character of waltzing, but it must 

 not be supposd that the dominant character is necessarily the 

 one nearest the normal type. Thus a short tail in cats is domi- 

 nant (somewhat imperfectly) to the ordinary tail; the appear- 

 ance of extra toes in poultry is dominant to the presence of the 

 normal four toes; hornlessness in cattle is dominant to the pres- 

 ence of horns. 



Among the many characters which are now known to exhibit 

 Mendelian inheritance, the following may be cited, the dominant 

 condition being named first in each case: Normal hair and long 

 Angora hair in rabbits and guinea-pigs; kinky hair and straight 

 hair in man; crest and no crest in poultry; bandless shell in the 

 wood-snail and banded shell ; yellow cotyledons in peas and green 

 ones; round seeds in peas and wrinkled forms; absence of awn 

 in wheat and its presence; susceptibility to "rust" in wheat and 

 immunity to this disease ; two-rowed ears of barley and six-rowed 

 ears; markedly toothed margin in nettle leaves and a slightly 

 toothed margin. Why one character should be dominant and 

 another recessive is not known ; a positive feature, like a banded 

 shell in the snail, may be recessive; and a negative feature, like 

 hornlessness in cattle, may be dominant. 



It should be noted that in many cases of Mendelian inher- 

 itance the dominance in the offspring is not complete; thus, if 

 black Andalusian fowls be crossed with white ones the progeny 

 are "blue" Andalusians a sort of diluted black. These "blue" 

 Andalusians do not breed true; when paired together they yield 

 50 per cent, "blues," 25 per cent, blacks, and 25 per cent, peculiar 

 whites splashed with grey. 



7 



The third fundamental idea in Mendelism is perhaps more 

 difficult to grasp than the others. Mendel supposed that the 

 hybrid between the tall pea and the dwarf pea produced two 

 kinds of germ-cells in approximately equal numbers one con- 



