DEVELOPMENT AND HEREDITY. 



CHAPTER I. 



EVOLUTION. LIMITS OF NATURAL SELECTION. — 



STATEMENT OF THE PROBLEM TO BE SOLVED. 



The present state of the theory of organic evolu- 

 tion may best be understood by a brief reference to 

 its history. Lamarck, the first to propose a theory 

 of evolution similar in scope to the present theory, 

 believed that effort, or the striving of an animal 

 after a certain thing, influenced its growth toward 

 the more ready attainment of that end. Thus use 

 of organs caused their further growth and develop- 

 ment, and disuse caused their degeneration. Every 

 change of environment necessitated a change in 

 the manner of activity, thus entailing changes in 

 the organism, which were cumulatively transmitted 

 to each succeeding generation, until finally two 

 widely separated generations in the same line of 

 descent bore no resemblance to each other. In 

 this way Lamarck supposed the diversity of animals 



