610 IMPROVEMENT OF LIVING THINGS BY MAN 



affects heredity, at least for a few generations. Professor 

 MacDougal of the Desert Laboratory of the Carnegie Institute 



has injected various 

 solutions of salts into 

 the ovaries of several 

 species of plants and 

 has found that the 

 seeds which grew pro- 

 duced plants which 

 differed in the plant 

 leaf and body of the 

 parent plant and these 

 variations persisted 

 through several gener- 

 ations. 



Practical Exercise 1. 



Using one of the books of 

 reference, make as long a 

 list as you can of modifica- 

 tions in plants brought 

 about by changes in the 

 environment. 



Animals and their 

 environment. Pro- 

 fessor Tower carried 



Wright Pierce 

 A tree beside a hillside. Notice how the sweeping winds 

 have caused the limbs to grow to one side of the tree. 



on a series of experiments with the potato beetle and found that 

 in some cases color changes brought about by the beetles living 

 in a changed environment were apparently handed down to the 

 future generations. Dr. Guyer induced eye defects in rabbits, 

 which were handed down to later generations of rabbits. Professor 

 Stockard's experiments in which he subjected guinea pigs to the 

 fumes of alcohol indicate that the young are profoundly affected, 

 many dying, and those which survived were undersized and nervous. 

 These effects were transmitted to the grandchildren. Dr. Hyde 

 reports that eyeless forms of fruit flies appear if the temperature 

 gets above a certain degree, while Dr. Morgan tells of certain 

 color changes in fruit flies that appear as soon as high humidity 

 becomes a factor in the environment. The developing eggs of 



