PREFACE TO THE FIRST EDITION 



The fundamental propositions behind this text — the platform, so to 

 speak, upon which it has been written — are as follows: 



1. Life has a chemicophysical basis. 



2. Life phenomena are the outgrowth of organization. 



3. The central fact in life is metabolism. 



4. Animals may be arranged in a progressive series with reference 

 to organization. 



5. The most complex animals are the most effective and also the most 

 efficient from a metabolic standpoint. 



6. Man, as the highest of animals, can learn by the study of animal 

 life the principles of the most effective living. 



7. He can also understand more fully his place in nature and can more 

 justly judge the actions of his fellows; this in turn may contribute to his 

 intellectual and spiritual development. 



8. Every problem concerned with living is essentially a biological 

 problem and capable of analysis and solution by the application of 

 biological principles. 



The book has been prepared for use as a class textbook, not as a work 

 of reference, and contains an amount of material which experience has 

 shown can be covered in three recitation periods a week for one year. 

 Since it will generally be used in beginning classes in which the majority 

 of the students are freshmen and sophomores, an effort has been made to 

 present the material in such a manner that it can be easily handled by 

 such students with normal preparation. In other words the idea is to 

 give the student an amount of material which he can cover in a way he 

 can understand. Also since the majority of the individuals in such 

 classes do not intend to specialize in the field of zoology, technicalities 

 have been minimized and emphasis placed upon the broader aspects 

 of the science and the general significance of the data presented, leaving 

 to subsequent courses the filling in of details for students majoring in 

 the subject. 



Feeling that the place to acquire a knowledge of the structure of 

 animals is in the laboratory and not in the classroom, the author has 

 reduced the amount of morphological material. In the case of those 

 types handled in both class and laboratory, the facts given here are 

 intended to tie the two together or to summarize the knowledge gained 

 in the laboratory. In the University of Nebraska the "types method" 



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