DOCTRINE OF EVOLUTION AND RELATED IDEAS 507 



ness to believe that man and his high mental and moral qualities 

 could have come about in this fashion. It is of course impossible 

 absolutely to prove that men or any other animals have thus 

 evolved from the lower orders because a perfect pedigreed suc- 

 cession can never be established. All that can ever be done is to 

 make it the most reasonable explanation for the conditions as 

 we find them. In reality it cannot make any material difference, 

 one way or the other, whether man developed or was created 

 outright. One does not escape or solve any final philosophical 

 problems in relation to the ultimate causes of the universe by 

 accepting or refusing to accept evolution. It is a method and 

 not a form of energy. No quality of man is any less valuable 

 or dignified under the assumption that it has grown than 

 under the assumption that it was made outright. Man's 

 social or moral place in the universe, like his place in American 

 society, is properly determined by what he really is and not by 

 the mere incident of the method of becoming. 



498. Topics for Library. — i. Find definitions of evolution. Write one of 

 your own. 



2. What are some of the arguments that have been offered to support the view 

 that " acquired " bodily characters are transmissible? 



3. State some arguments that have been advanced against the view? 



4. State briefly Galton's law of heredity. 



5. What does the gradual development of the physical, mental, and moral 

 nature of the human individual suggest? 



6. State DeVries' doctrine of "mutation" in a brief way. 



7. State Johanssen's "pure line" theory. 



8. State the modern usage of the term mutation. 



9. What is meant by "genotype?" By phenotype? Can we change the 

 genotype by changing the phenotype? 



10. Discover some of the facts about the location and arrangement of the 

 genes (or determiners) in chromosomes. What does linkage mean in this con- 

 nection? i 



11. Mention instance of "crossing over" in Mendelian inheritance. Evidence 

 for it? How is "crossing over" supposed to take place? 



12. How is sex determined, in accordance with the Mendelian theory? What 

 evidences do we have that nutrition or other environmental factors enter into sex 

 determination? 



