538 HEREDITY 



yielding best can be determined. In this way one can also 

 determine whether or not newly introduced strains hold up in 

 yield. 



The chief objection to this method is that the heritage of the 

 individuals is too much neglected, and fundamentally heredity 

 is a matter pertaining to individuals rather than to masses of 

 individuals. A mass of individuals, such as a field of Wheat, 

 Corn, or Oats, is a mixture of individuals differing in their heritage, 

 and in order to discover the laws of heredity by studying a group 

 of individuals, the individuals of the group must be alike in their 

 heritage and this is seldom the case. It is obvious that finding 

 the average of a character in a group of individuals tells us very 

 little about heredity unless the individuals are alike in what 

 they have inherited for the character. 



The method now mostly used is the pedigree culture method. 

 In this method the attention is centered upon the individual and 

 not upon groups of individuals. By this method the characters 

 of each parent are carefully studied, the pollination or breeding 

 carefully controlled, and each individual of the progeny is care- 

 fully compared with its brothers and sisters and with its parents 

 in respect to the characters being studied. Throughout a number 

 of generations the characters of each individual are carefully 

 studied. This is the method introduced by De Vries in the study 

 of variations, and by Mendel in the study of heredity. This is 

 the only method that has yielded satisfactory results. The 

 pedigree culture method is now universally used and De Vries and 

 Mendel are regarded as having made a very valuable contribution 

 to science in demonstrating the importance of this method. 



Galton'sLaws of Heredity. — Francis Galton (1822-1911), a 

 cousin of Charles Darwin, was one of the foremost in studying 

 heredity by the statistical method. He was much interested in 

 applying the principles of heredity to the improvement of the 

 human race, and suggested the term -'Eugenics" for this phase 

 of the subject. One of his laws which he announced in 1897, is 

 known as the "Law of Ancestral Inheritance." According to 

 this law the individuals of an offspring receive on the average, 

 half of their heritage from their parents, one fourth from their 

 grandparents, one eighth from their great grandparents, and 

 so on. Another law he formulated is known as the law of 

 "Filial Regression." This law may be illustrated by comparing 



