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that their only chance of making a breed pure for any character, 

 is to have a study made of the genetic factors, necessary for 

 this character, and by breeding from homozygotes only. It is 

 after some study comparatively easy to find the necessary indivi- 

 duals which can be used for testing the stock. It will have to 

 become understood by breeders, that in judging an animal for 

 stock-purposes, they must not in the first place ask for the quali- 

 ties of its parents, but rather inquire after the quality of all of 

 its children from animals of different quality. As in the stud- 

 books the inferior individuals are for different reasons not 

 inscribed, they give an utterly false idea of the history of the 

 variety, and they have hardly any value, even for the study of 

 less important genetic factors. But as in animals it is practically 

 never required to produce a new biotype, a general understanding 

 of Mendelism, and the use of testmatings can be of enormous 

 benefit. It will have to be the aim of biologists to devise Systems 

 of breeding, which can be followed by the practical men „by 

 rule of thumb" as the present Systems are now, if they will pro- 

 duce a lasting effect on the amelioration of the breeds. 



Whereas the work of manipulating the genetic factors of 

 plants can be done for the whole country at one central Station? 

 the practical men getting their pure seeds directly from the Station or 

 indirectly through the seed-growers, and a more general know- 

 ledge of the principles is relatively superfluous to them, in the 

 breeding of animals, nearly everybody using them must necessa- 

 rily breed them. If therefore ; in the case of plants, it will suffice 

 for any country, if one or two men, well versed in this work, 

 will apply themselves to it, it is of the utmost importance that 

 practical breeders of animals should be taught to^ understand 

 how to choose what they want. 



In man the relation of genetic and non-genetic factors is 

 perhaps still less understood than in animals and plants. And 

 here, as everywhere when positive knowledge is scarce, personal 

 beliefs on the subject are all the more imposing. One man beliefs 

 that to ameliorate mankind and social conditions, it will be 

 necessary to prohibit by legislation some special types of marriages. 

 This idea goes with the other, that conditions outside the germ 

 have only an unsignificant influence on the making of a man's 

 character. Thus have we lately heard a curious tale of an experi- 

 ment, in which a large number of boys and girls from criminal 



