E^TRODUCTION 



11 



tion and behavior, the relations of animals 

 to their environment (ecology), the geo- 

 graphic distribution of animals (zoogeogra- 

 phy), heredity (genetics), reproduction and 

 development, the origin and history of ani- 

 mal life (organic evolution), and the history 

 of zoology. 



Science and its methods 



One of the objectives of a course in zool- 

 ogy is to gain an understanding of the 

 scientific method. The method of science 

 involves primarily (1) being aware that a 

 problem exists, (2) formulating a supposi- 

 tion (hypothesis) on the basis of a rela- 

 tively small amount of information, (3) 

 testing the correctness of the hypothesis by 

 securing more facts by direct observation or 

 experimentation, (4) arranging the facts 

 observed in some orderly manner to deter- 

 mine relationships, and (5) drawing valid 

 conclusions. It is by this logical procedure 

 that most of our zoological principles have 

 been developed. 



The scientific method involves skillful 

 handling of the material being studied, care- 

 ful observations, controlled experiments if 

 possible, close attention to detail, clear 

 thinking in drawing conclusions, and the 

 modification of conclusions when further 

 facts make this necessary. This is the method 

 of discovery. 



Attitudes are also very important in solv- 

 ing problems by the scientific method. They 

 include (1) intellectual honesty, that is, 

 freeing oneself of prejudice and admitting 

 an error when facts indicate that there is 

 one, (2) openmindedness about a subject, 



(3) cautiousness in reaching conclusions, 



(4) a willingness to repeat experiments (the 

 facts obtained by one experimenter must be 

 verified by others as well as himself, so that 

 conclusions are confirmed), and (5) vigi- 

 lance for the occurrence of possible flaws in 

 hypotheses, theories, evidences, and conclu- 

 sions. 



Anyone can make discoveries in zoology 



with very little training, and few human ex- 

 periences can furnish such a thrill as that 

 of making an original discovery. 



Principles of zoology 



Zoological principles are scientific theories, 

 facts, and laws of wide application. It is 

 possible to make a list of zoological princi- 

 ples and to discuss them with the aid of 

 photographs or laboratory material, but the 

 best method of learning them is to study 

 animals and deduce principles after a suf- 

 ficient amount of original data has been 

 accumulated. This book has been prepared 

 with this aim in view. After each chapter has 

 been studied and the appropriate laboratory 

 studies have been completed, a careful re- 

 view should be made of the knowledge thus 

 obtained, and a list of zoological principles 

 prepared. For example. Chapter 3 is devoted 

 to the class Sarcodina of the phylum Pro- 

 tozoa, and the amoeba is employed as a 

 typical species. After studying this species 

 and possibly other Sarcodina in the labora- 

 tory and reading the account in this book, 

 one of the principles which will be evident 

 is that every member of the class Sarcodina 

 consists of a single cell. From this principle 

 we may derive the subordinate principle 

 that among the Sarcodina a single cell car- 

 ries on all of the physiologic processes nec- 

 essary for maintaining the individual and 

 the race. When all classes of the Protozoa 

 have been studied in the chapters that fol- 

 low, principles that are applicable to the 

 entire phylum may be deduced. Later in 

 the course, principles that apply to several 

 phyla and finally to the entire animal king- 

 dom may be formulated. 



Zoology and human progress 



The study of animals has been of great 

 intellectual and practical value to man. It 

 has enabled him to recognize the unity of 

 all living things and to determine his place 

 in nature. Zoological knowledge has made it 



