INTRODUCTION 



THE CLASSIFICATION OF ANIMALS is Still Very much a field in which dis- 

 covery and revision are continuing, even after two hundred years of 

 study. The importance of classification in biology increases every year, 

 because the experimental and practical fields find increasing need for 

 accurate identification of animals and for understanding of compara- 

 tive relationships. 



At least one outstanding biologist has opposed pubUcation of 

 this new classification on the ground that it would be accepted as final, 

 the classification, and would tend to make students think that all higher 

 classification is finished. The intention of the compiler is just the op- 

 posite. Just as this classification is different in detail from all previous 

 ones, so will future editions be still different, as we learn more about 

 the comparative features of animals. 



It is anticipated that every new edition will spur students of the 

 individual groups to propose improvements. It is therefore planned to 

 issue corrected editions whenever appropriate. The very appearance of 

 these subsequent editions will emphasize the growth of understanding 

 of animal groups. 



Only one ostensibly complete classification of animals, living and 

 fossil, has been published in recent years. That classification, by A. S. 

 Pearse of Duke University, is a good one, based on the views of many 

 specialists. Certain mechanical faults make it less usable than it should 

 be, and the need for revision gave the original impetus to preparation 

 of the present classification. Because Pearse did not usually indicate the 

 source of his arrangements, he is not here cited as an authority. Never- 

 theless, the two classifications are basically very similar. No other single 

 classification has been found that agrees so closely with the conclusions 

 of the present study. 



It should be emphasized that, within certain limits, this classifica- 

 tion is not a simple compilation of the views of specific workers. In 

 nearly all details, choices have been made between conflicting schemes 



