THE PRACTICAL VALUE OF GENETICS 353 



last few years has a method been devised for the artificial control 

 of mating, and this has not yet been widely used. 



Selection has been practiced for various characters in the honey- 

 bee, such as light color, industry based on the amount of honey 

 stored, color of wax produced, temper, and swarming propensity. 

 By rearing queens only from mothers whose colonies best expressed 

 the desired characters and by restricting the production of drones 

 (males) in other colonies as much as possible, many distinct 

 strains of Italian bees have been produced. Some are called 

 three-banded leather-colored Italians, others golden Italians be- 

 cause they very nearly lack the black abdominal bands and are 

 pale in color. Some sting readily while others are mild tempered 

 and sting only when conditions for handling bees are very unfavor- 

 able. A most desirable result of selection is the reduction or 

 elimination of swarming instinct, which is the bee-keeper's greatest 

 source of annoyance. Some strains swarm readily and often, while 

 others will go through a season under conditions entirely favorable 

 to swarming without attempting it. 



Line Selection. The fundamental principles of Mendelian in- 

 heritance disclose the necessity of knowing the genotypic organi- 

 zation of an individual for accurate control of succeeding genera- 

 tions. Even before Mendel worked out his laws the value of 

 his discoveries in relation to selection was anticipated by the work 

 of Vilmorin, near the middle of the nineteenth century. He selected 

 single plants whose offspring were isolated for comparison. The 

 principle was later applied by various plant breeders, and in the 

 hands of Hjalmar Nilsson at the experiment station of the Swedish 

 Seed Association at Svalof it has produced many valuable strains 

 of wheat, peas, potatoes and other plants. The method is also 

 known as pedigree breeding. 



The obvious value of line selection is that the isolation of 

 offspring of single individuals is much more likeh^ to produce a 

 uniform variety. Even superficially identical individuals, as we 

 have seen, may be genotypically different and therefore capable 

 of producing different offspring. 



Genotypic Selection. While any method that takes into ac- 

 count the character of the succeeding generations in relation 

 to their known ancestry is to some extent genotypic, in the strict 

 sense, this term should apply to the type of selection which is 

 used in connection with known facts of Mendelian inheritancBo 



