MENDELISM 139 



v.— RESULTS, 



The discoveries of Mendelian phenomena have opened 

 up new vistas to our inquiries on Heredity, which have 

 been groping so long in the dark. Not only scientific 

 theories of the greatest consequence flow from the facts 

 ascertained, but also practical results of far-reaching 

 importance. Not unfittingly has R. C. Punnett compared 

 the position we have now attained in regard to the 

 knowledge of Inheritance with the discovery of the atomic 

 theory in Chemistry by Dalton. We are at last on the 

 first rung of the ladder leading to an exact knowledge of 

 the phenomena of heredity. 



It has become evident that the individual is an entity 

 made up of hereditary unit-characters. The aggregate 

 of such units forms the individual. During the process of 

 inheritance the units segregate, and by recombination form 

 new individualities. And this is the most important 

 result accruing to the art of the practical breeder. He can 

 now, by judicious crossing, produce new strains — not blindly, 

 as before, but with an exact knowledge of what he wants 

 and what he can achieve. We have seen, for instance, 

 that by crossing two varieties a dihybrid can be produced 

 which in the next generation reproduces, not only the 

 two original parent forms, but also, by reuniting the 

 parental characters in different combinations, two novel 

 forms. We have further seen that within this number of 

 individuals of the F2 generation there are four true breeding 

 types which, by careful separate breeding, can be recognized 

 and fixed in the next generation. It is clearly shown that, 

 if this is done scientifically on Mendelian principles, only 

 two generations of breeding are required to produce a new 

 and stable form. Furthermore, it has become clear that 

 there is no fear of the new forms being swamped by inter- 

 crossing, as new foiTns and old ones breed out separately, 

 and breed true. 



The theory of Dai-win that evolution takes place by small, 



