239 
that tlieir 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 niust 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 tuen „by 
rule of thumb" as the present Systems are now, if they Avill 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- 
Icdge 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 
necessjiry to prohibit by legislation some special types of marriages. 
This idoa goes with the other, that conditions outside the germ 
have only an unsignificant influence on the making of a man 's 
charactcr. Thus have we lately lieard a curious talc of au experi- 
ment, in which a hirgc nuniber of boys and girls fmui criniinal 
