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SUBJECT MATTER OF GENETICS 



Materials of Heredity and Their Operation 



Genetics searches for the answer to certain questions 

 concerning organisms. How does it happen that living 

 things differ? How are the differences brought about? How 

 does it happen that some Hving things resemble certain 

 others, while some are very unlike? What brings about the 

 many degrees and kinds of similarity and difference among 

 living things? 



The questions that are dealt with in genetics may be 

 illustrated concretely for man. How does it happen that 

 some are men, some are women? How does it happen that 

 some are tall, some are short; some are stout, some are 

 thin? How is it brought about that some are lighter, some 

 darker in complexion? How does it happen that some have 

 blue eyes, some gray eyes, or brown or black eyes? There 

 are differences of all sorts, great and small, in form of the 

 features, size and shape of the nose, distance apart of the 

 eyes, and in hundreds of other peculiarities of the face and 

 body. What are the causes of these? 



Further, some individuals are strong, while others are 

 weak. Some are healthy, some are sickly. Some individuals 

 suffer from tuberculosis, from cancer, or from other dis- 

 eases, while others are immune. What are the grounds for 

 such diversities? Still more important are differences in 

 "minds," differences in behavior. Some persons are feeble- 

 minded, not able to care for themselves or do the ordinary 



