OLD TYPES AND NEW 



not necessarilyj^oLated by this^ procedure. The conse- 

 quence is that Burbank's method cannot be utilized 

 in animal breeding to any great extent where the main- 

 tenance of a desirable strain by asexual propagation 

 is out of the question. 



It will be seen that this method is fortuitous and to 

 a certain extent unscientific in that no one can repeat 

 the exact conditions of the experiment and arrive at 

 the same results. It depends upon the chance mixing 

 up of a large number of possibilities and then in not 

 being distracted or blinded by the good while selecting 

 the best. In the hands of a skilful plant breeder 

 with unlimited resources at his command it may 

 result in much practical achievement, but it does 

 not particularly illuminate the path of other breeders 

 who wish to repeat the experiment. It is after all 

 selection of phenotypes and, therefore, forever open to 

 error, since phenotypes do not always indicate what 

 the behavior of their constituent genotypes will be in 

 heredity. 



b. The Method of Mendel 



The method of Mendel, like the foregoing, depends 

 upon hybridization with the difference that the desired 

 combination is sought directly by definite predetermined 

 crosses, according to the expectations of the Mendelian 

 ratios, rather than through the random result of for- 

 tuitous combinations. It is a method which has been 

 rendered possible by the determination of Mendel's laws 

 of dominance, and of the independence and segregation 

 of unit characters which give to the experimental 



