CHAPTER XX 
THE SCOPE AND METHODS OF GENETICS 
H. H. N. 
DEFINITIONS 
“Genetics is the science which seeks to account for the resem- 
blances and the differences which are exhibited among organisms 
related by descent.”—Babcock and Clausen. 
“Genetics may be defined as the science which deals with the 
coming into being of organisms. It does not refer, however, to the first 
creation of organic beings, but rather to the present every-day creation 
of new individuals or new races. It refers particularly to the part that 
parent organisms have in bringing new organisms into being and to the 
influence which parents exert on the characteristics of their offspring. 
In this sense it is nearly equivalent to the term heredity.”—W. E. 
Castle. : 
“Heredity may be defined as organic resemblance based on de- 
scent.””—W. E. Castle. 
“Heredity is commonly defined as the tendency of offspring to 
develop characters like those of the parents.”—Babcock and Clausen. 
THE SCOPE AND METHODS OF GENETICS 
Genetics is the study of evolution from a new point of view. The 
great evolutionists of the past were devotees of the inductive method 
in science which consists of collecting data and devising theories to 
explain the data. None of the older evolutionists attempted to put’ 
their theories to experimental tests. Thus their theories, though in 
some respects well founded, have never reached that stage of scientific 
proof which involves the use of the experimental method. The new 
method in evolution is that of experiment under controlled conditions. 
If new characters arise before the eyes of the investigator in a known 
stock of animals or plants and the factors responsible for the change 
are known and are capable of control, it may be said that man has 
actually taken a hand in evolution. If new characters arise in a 
known stock, but from an unknown cause, the course of the new 
character in inheritance may be controlled and some knowledge of the 
287 
