PREFACE TO FIRST EDITION 



The Elasmobranch Fishes are, I believe, unsurpassed as material on whicli 

 to study the fundamental plan of the vertebrate body. The ease with which a 

 large, cartilaginous form may be dissected makes a study of its systems of 

 organs a relatively simple matter, and the comparative simplicity of most of 

 the systems shows that at least some of the present-day Elasmo])ranchs closely 

 approximate the early vertebrates. 



The importance of the shark as a type for classroom study has, I think, not 

 been generally appreciated in this country. This has been due in part to the 

 difficulty of obtaining specimens in centers removed from the seaboard; in 

 part, it has been due to the paucity of available literature. This I say in face 

 of the fact that an abundant literature in practically all languages exists. I 

 have attempted to remedy this latter ditficulty by adding to each chapter a 

 working bibliography. 



In my studies of the Elasmobranchs I have been fortunate in having at hand 

 perhaps the most generalized of these fishes, Heptanchus maculatus. In addi- 

 tion to a study of the systems of organs in this and in other forms, I have at- 

 tempted to collect and unify the work done by many workers on the various 

 types. These combined studies I present with the hope that they will serve as 

 a guide for undergraduate students of college grade, and at the same time be 

 sufficiently inclusive to be used as a book of reference on the entire subject. 



I am indebted to the Scripps Institution for Biological Research for liberal 

 support during five summers at La Jolla, and to the Research Board of the 

 University of California for a grant in the final finishing of the plates. I am 

 further indebted to many students who have helped me. Among them I single 

 out Duncan Dunning, who, as a sophomore and junior student, made many of 

 the most important drawings in the book. 



J. Frank Daniel 

 Berkeley, California, 

 January 16, 1922. 



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