RELATIONS AND SURROUNDINGS. 151 



become adapted to conditions in the environment which 

 do not have power of influencing life. 



4. It is believed that adaption between animals and 

 their surroundings has been progressive; that is, that the 

 adaptation is on the whole more exact and successful in 

 the higher than in the lower animals. 



5. Animals are adjusted to the environment because 

 they must be. The environment may produce the 

 necessary changes directly, or it may merely select those 

 animals whose hereditary characteristics are most ad- 

 vantageous and eliminate those which are not suited to 

 the conditions, or it may do both. In any event it is 

 the environment which finally determines the adaptation. 



165. Topics for themes in Zoology or English. 



1. What is the difference between an individual and a 

 colony? Is the "Portuguese man-of-war" an individual? 

 Evidences? 



2. Can you prove from your own observations that 

 the use or disuse of an organ produces changes in it. 

 Give illustrations. 



3. Have you ever observed any changes in animals 

 which were due to the action of the environment? 



4. Can you illustrate what is meant by heredity by 

 a series of facts of your own observation? 



5. Are the offspring of the same parents alike? How 

 much variety have you ever noticed? Did they inherit 

 their differences or acquire them? 



6. Does the mother have any more hereditary in- 

 fluence on the offspring than the male? Evidences. 



7. Can offspring be unlike their parents through the 

 influence of heredity? 



8. Cite some instances of voluntary association which 



