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 denned 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 

 hi science which consists of collecting data and devising theories to 

 explain the data. None of the older evolutionists attempted to put 

 then- theories to experimental tests. Thus their theories, though 

 hi some respects well founded, never reached that stage of scientific 

 proof which involves the use of the experimental method. The new 

 method hi evolution is that of experiment under controlled conditions. 

 If new characters arise before the eyes of the investigator hi 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 



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