CONTENTS. 



?AGE 



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 Cgxenterata, 102 



* IV. — The Tcrbellaria, the Rotifera, the Trematoda, and the 



Cestoidea, 157 



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



Gephyrea, 189 



YI. — 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 CH.ETOGNATHA, THE NeMATOIDEA, THE PHYSEMARIA, 

 THE ACANTHOCEPHALA, AND THE DlCYEMIDA, . . . 534 



XT!. — The Taxonomy of Inyertebrated Animals, .... 561 

 Index, 589 



