v iii PREFACE TO THE REVISED EDITION. 



to surrender these views. My reasons for adhering to them 

 will be found in notes to the ends of Chapters III and IV 

 in Fart IV, and in Appendix D 9 . 



On now finally leaving biological studies, it remains only 

 to say that I am glad I have survived long enough to give 

 this work its finished form. 



Brighton, 



October, 1899. 



