PEEFACE TO FIRST EDITION 



There has come into being a considerable number of relatively 

 short but fundamental zoology courses. Often they are given in a 

 single semester. Such courses usually involve rather intensive lab- 

 oratory study of the systems of one or two vertebrate forms, a few 

 selected invertebrates, and a number of special relationships as para- 

 sitism, reproduction, development, etc. The recitation or theory 

 portion of such a course is ordinarily concerned with some coordina- 

 tion and summary of the selected materials treated in the laboratory, 

 but perhaps more particularly with the lessons in principles which 

 may be drawn from them. 



It is the presence of this type of course in a number of different 

 zoology or biology departments Avhich has prompted the organiza- 

 tion of the present book. It is the purpose of the author to bring 

 into the book the essential fundamentals which every zoology stu- 

 dent should have, regardless of the length of the course he happens 

 to take. 



It is likely true that the majority of the students taking elemen- 

 tary zoology will have only that one course in the field and for that 

 reason some emphasis is placed on the economic aspect, on the human 

 relation, and on the principles involved. It is assumed that the 

 teacher will elaborate upon the details of particular topics of interest 

 to the class beyond the limitations of detailed information contained 

 in this volume. 



The arrangement of the chapters has been placed in an order 

 which seems logical. However, the chapters are written in such a 

 way that the teacher may change the order with no difficulty. Since 

 this is true, the teacher has some option in the possibility of striking 

 a workable combination of 'Hypes" and ''principles" material as 

 well as balance in laboratory -lecture program. 



The author is indebted to, and extremely grateful for the coopera- 

 tion of, the following who have contributed to the manuscript: 



J. Teague Self, University of Oklahoma, Earthworm 



Elmer P. Cheatum, Southern Methodist University, Fresh-Water 

 Clam and Snail 



Vasco M. Tanner, Brigham Young University, Locust 



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