Preface 



ganoids does not concern us here. On the bot- 

 tom the external skeleton would be fostered. 

 Here, as In most cases, though perhaps not in 

 all, habit and natural selection work together 

 toward the same goal. The one can accomplish 

 what the other may not do. The Neo-Lamarck- 

 lan recognizes the value of both habit and struc- 

 ture; the Neo-Darwinian will not deny this 

 action and tendency of selection. 



While writing the book I have been continu- 

 ally reminded of pleasant moments passed in dis- 

 cussing these and other questions with pupils of 

 successive classes. If the book has any value, a 

 large part of it is due to the stimulus of their 

 interest. If it can arouse something of the same 

 Interest, and now and then a healthy opposition 

 In other minds, I will be more than content. 



J. M. T. 



