PREFACE Vll 



chapters on insects. Dr. L. J. Cole of the University of 

 Wisconsin has had the exceptional patience to read several 

 of the chapters in the almost illegible script in which they 

 were originally written. I wish to thank Prof. J. S. 

 Kingsley and Henry Holt and Co. for permission to use 

 figures from Kingsley's translations of Hertwig's Zoology. 

 Dr. Paul Carus has very kindly permitted me to use 

 several cuts from Romanes' Darwin and After Darwin 

 issued by the Open Court Publishing Company. To 

 Dr. B. W. Evermann I am indebted for photographs of 

 several groups of mammals and birds in the museum of 

 the California Academy of Sciences. Most of all I am 

 indebted to my wife for help in many ways during the 

 preparation of this work. 



S. J. H. 

 BERKELEY, CALIF. 



