154 MENDELISM CHAP. 



her. We know that bay is dominant to chestnut, 

 and that if a homozygous bay stallion is used a bay 

 foal must result. In his choice of a sire, therefore, 

 the breeder must be guided by the previous record 

 of the animal, and select one that has never given 

 anything but bays when put to either bay or chest- 

 nut mares. In this way he will assure himself of a 

 bay foal from his chestnut mare, whereas if the record 

 of the sire shows that he has given chestnuts he will 

 be heterozygous, and the chances of his getting a 

 bay or a chestnut out of a chestnut mare are equal. 



It is not impossible that the breeder may be 

 unwilling to test his animals by crossing them with 

 a different breed through fear that their purity may 

 be thereby impaired, and that the influence of the 

 previous cross may show itself in succeeding genera- 

 tions. He might hesitate, for instance, to test his 

 polled cows by crossing them with a horned bull for 

 fear of getting horned calves when the cows were 

 afterwards put to a polled bull of their own breed. 

 The belief in the power of a sire to influence sub- 

 sequent generations, or telegony as it is sometimes 

 called, is not uncommon even to-day. Nevertheless, 

 carefully conducted experiments by more than one 

 competent observer have failed to elicit a single shred 

 of unequivocal evidence in favour of the view. Until 

 we have evidence based upon experiments which are 

 capable of repetition, we may safely ignore telegony 

 as a factor in heredity. 



Heterozygous forms play a greater part in the 

 breeding of animals than of plants, for many of the 

 qualities sought after by the breeder are of this 

 nature. Such is the blue of the Andalusian fowl, 



