vi PREFACE 



Clung and Dr. E. Carothers, Cytology; Dr. A. B. Dawson, Blood; 

 Dr. A. C. Redfield, Respiratory Pigments; Dr. A. M. Lucas, Ciliary 

 Action; Dr. Edwin Linton, Dr. C. A. Kofoid, and Dr. H. W. Stunk- 

 ard, Platyhelminthes; Dr. Frank Smith and Dr. Earl Martin, 

 Annelida; Dr. N. A. Cobb, Dr. M. C. Hall, Dr. C. A. Kofoid, 

 Nematoda; Dr. R. S. Lynch, Dr. H. M. Miller and Dr. H. B. Smith, 

 Trochelminthes; Dr. B. H. Grave and Dr. E. D. Crabb, Mollusca. 

 Dr. C. M. Child, Dr. Austin Clark and Dr. William Patten have 

 kindly furnished concise summaries of their important theories. 



With the aid of their staffs the following Librarians, Mr. George 

 Osborn, Rutgers University, Dr. L. D. Arnett, West Virginia 

 University, and Mrs. T. H. Montgomery, Marine Biological Lab- 

 oratory, have so contributed to the accuracy of the text by their 

 tireless efforts in furnishing reprints, references and books that they 

 deserve much of the credit for such corrections of errors made by 

 senior scholars as the author may have been able to make. 



Dr. W. H. S. Demarest, Dr. F. B. Trotter, and Dr. J. R. Turner, 

 the University Presidents under whom the writer enjoyed every 

 opportunity for effective teaching that these able executives could 

 possibly furnish, should be heartily thanked for their aid. 



The writer also wishes to acknowledge his indebtedness to: the 

 late Dr. C. W. Hargitt, Dr. W. M. Smallwood, Dr. C. F. Hodge, Dr. 

 A. M. Reese, Dr. F. R. Lillie, Dr. E. G. Conklin, Dr. C. B. Daven- 

 port, Dr. T. J. Headlee, Dr. Gary Calkins and Dr. C. E. McClung. 

 By their encouragement, these men have been largely responsible 

 for the vigor and enthusiasm with which the writer has been able 

 to study zoological problems and to teach his subject for more than 

 twenty years. 



General criticism has been offered by Dr. J. A. Dawson, Dr. 

 Mary MacDougall, Dr. W. C. Curtis, Dr D. H. Tennent, Dr. 

 Charles Packard, Dr. R. A. Budington, Dr. W. L. DoUey, Dr. 

 Oscar Richards, Dr. J. W. McGregor, Dr. J. W. Mavor, Dr. Leigh 

 Hoadley, and many others. 



In the preparation of the glossary. Professor A. J. Hare of the 

 West Virginia University has assumed the responsibility for the 

 Greek and Latin derivations of the words used. 



The drawings were made by Mr. W. J. Moore, Mrs. Helena 

 Lammers and Mr. Norris Jones. 



F. E. C. 



Woods Hole, Mass., 

 November 1931 



