PREFACE 



Curtis and Guthrie's Textbook of General ^oology has been a standard work 

 in its field through three decades and four editions. The withdrawal of Pro- 

 fessor Winterton C. Curtis from active participation in a further revision, 

 together with the rapid development of many areas of zoological knowledge 

 and interpretation, has made the preparation of an essentially new book 

 preferable to the issuance of a fifth edition in the Curtis and Guthrie series. 

 Nevertheless, those familiar with "Curtis and Guthrie" will immediately 

 recognize how much this book owes to its predecessors, in content, organiza- 

 tion, and emphasis. In general, we have endeavored to preserve the features 

 of the Curtis and Guthrie texts that have proved successful in teaching prac- 

 tice and to revise and amplify the parts that progress in zoology has made 

 inadequate. 



This is not an easy, superficial book. We are convinced that giving the 

 student an insight into the great depth and richness of zoology may awaken 

 his interest and so fire his imagination and curiosity that he will find the 

 subject worthy of further study. Even if he is a terminal student, contem- 

 plating no studies in zoology beyond his introductory course, leading him 

 into some of the more profound aspects of the subject will make his limited 

 experience more rewarding. His textbook should not be one in which he 

 merely performs assigned readings; he should have a book he can read with 

 enjoyment, one that gives him a broad foundation and background for the 

 sometimes narrow and necessarily restricted view of zoology which he glimpses 

 in classroom and laboratory. On the other hand, there are limits to the 

 amount of factual information and learned terminology to which students 

 should be subjected in introductory textbooks. 



We do not believe, as some zoologists do, that emphasis on anatomy, and on 

 the phylogenetic relationships which can often be inferred from structural 

 similarities, constitutes an outmoded approach to zoology. Although the 

 most dynamic recent advances have stemmed from physiological studies, an 

 understanding of structure is prerequisite to an appreciation of the functions 

 of organisms. Our objective has been to write a book in which functional 

 aspects are emphasized, but in which they are made coherent and intelligible 

 by a full exposition of the anatomical features involved. Further, we have 



