CONTENTS 



PAGE 



Preface, 3 



Introduction : The General Principles of Biology, . 9 



Chap. I. — The Distinctive Characters of Animals, . . . .44 



II. — The Protozoa, 73 



III. — The Porifera and the Ccelenterata, 102 



IV. — The Turbellaria, the Rotifera, the Trematoda, and the 



Cestoidea, 157 



V. — The Hirudinea, the Oligoch^ta, the Polych^ta, the 



Gepiiyrea, 189 



VI. — The Arthropoda, 219 



VII. — The Air-breathing Arthropoda, 320 



VIII. — The Polyzoa, the Brachiopoda, and the Mollusca, . . 389 



IX. — The Echinodermata, 466 



X. — The Tunicata or Ascidioida, 510 



XI, — The Peripatidea, the Myzostomata, the Enteropneusta, 



the CHiETOGNATHA, THE NeMATOIDEA, THE PhYSEMARIA, 

 THE AcaNTHOCEPHALA, AND THE DiCYEMIDA, . . . 534 



XII. — The Taxonomy of Invertebrated Animals, . . . .561 

 Index, 589 



