24 DEVELOPMENT AND HEREDITY. 



tions ? In attempting a solution of this problem, we 

 must inquire how matter is affected by the forces 

 which act upon it, and especially how living matter 

 is affected by the forces of its environment. We 

 must study the nature of living matter and the 

 source and transformations of its energy. Finally, 

 we must consider the natural operation of this pecu- 

 liar form of matter under the action of the forces 

 of the environment. 



