CONTENTS 



Page 



[ntroduction 1 



Chapter 



I. The Living Animal 3 



II. The Test 9 



III. Collecting and Preparing Material .... 19 



IV. Methods of Study 23 



V. Economic Use 31 



VI. Geographic Distribution 36 



VII. Geologic Distribution 42 



VIII. Classification 47 



IX. Systematic Arrangement to Genera with Keys . 51 



X. Trimorphism 357 



IX. Bibliography 361 



Index . . . ■ . . 393 



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