342 MUTATIONS 



changes. Other insects, such as butterflies and grasshoppers, have 

 been known to produce mutants by a decided change in tempera- 

 ture, food, and recently by the use of the X-ray. The treatment 

 of parent fruit flies and mice with X-ray and radium rays has 

 caused them to produce offspring with somewhat malformed 

 bodies. These peculiar characters were handed down to the next 

 generations. The germ plasm had been affected. It would seem 

 that in some way the germ plasm is affected by the change in 

 the conditions of the environment, causing mutations to appear 

 in the second generation. It is not conclusively known whether 

 a decided change in environment has ever produced mutants in 

 nature as it has been done under experimental conditions in the 

 laboratory. 



Questions and Suggestions 



1. State the doctrine of continuity of germ plasm. How old is 

 germ plasm? 



2. What are mutations ? Give examples. 



3. What is the relation of mutations to heredity ? 



4. What part did Hugo de Vries play in developing the theory of 

 germ plasm ? 



5. Give three theories concerning the causes of mutations. 



6. Discuss Professor Morgan's work with fruit flies. 



7. Discuss Doctor Tower's work with potato beetles. 



8. Give a library report on the biography of August Weismann. 



9. Look up in a recent science book or magazine and report on the 

 experiments that are now being carried on concerning mutations. 



