8 PREFACE 



Amphibia, and assisted with Marine Zoology; Leo T. Murray, Baylor 

 University, assisted by James E. Blaylock, Ranger Junior College, 

 Reptilia; Helen Joe Talley, University of Oklahoma, collaboration 

 on Regulatory Glands; T. C. Byerly, United States Bureau of Animal 

 Industries, Ayiimal Regeneration; Titus C. Evans, University of 

 Iowa, Medical College, Biological Effects of Radiation; Willis Hewatt, 

 Texas Christian University, A^iimal Distrilution, and assisted with 

 Marine Zoology; A. 0. Weese, University of Oklahoma, The Animal 

 and Its Environment ; Sewell H. Hopkins, Texas Agricultural and 

 Mechanical College, Animal Parasitism ; J. G. Burr, Texas Game, 

 Fish, and Oyster Commission, marine data; Walter P. Taylor, Texas 

 Cooperative Wildlife Service and United States Bureau of Biological 

 Survey, Wildlife Conservation; A. Richards, University of Okla- 

 homa, Comparative Embryology ; Frank G. Brooks, Cornell College, 

 Genetics and Eugenics; Iva Cox Gardner, Baylor University, Animal 

 Behavior; W. M. Winton, Texas Christian University, Paleontology . 



To Mr. Ivan Summers goes immeasurable credit for the excellent 

 art work he has put into this edition. Dr. Titus Evans, of the 

 University of Iowa, Medical College, has also been of great service 

 with his excellent talent in creating illustrations. Mrs. Ruth M. 

 Sanders, Miss Joanne Moore, and Mr. Edward O'Malley have each 

 assisted by contributing certain illustrations. The drawings used in 

 Chapter XLII on Genetics and Eugenics were made by Miss Betty 

 R. Smith of Cornell College. The author is grateful to all of these 

 individuals for their valuable services. 



The author wishes to acknowledge also the friendly and helpful 

 advice which has been offered by Professors D. B. Casteel, T. S. 

 Painter, and E. J. Lund of the University of Texas, and Professor 

 Asa Chandler of Rice Institute. Finally, appreciation is expressed to 

 Baylor University for the cooperation which has made the writing of 

 this book possible. 



George E. Potter. 



Waco, Texas. 



