xiv CONTENTS 



PAGE 



Phylum Protozoa — continued. 



Class V. Infusoria 88 



1. Example of the Class — Parametrium caadatum .... 88 



2. Classification and General Organisation 91 



Systematic Position of the Example 91 



Further Remarks on the Protozoa . . . . - . . . 101 



SECTION III 



Phylum and Class Porifera [Parazoa] 105 



1. Example Sf the Class — Sycon gelatinosum 105 



2. Distinctive Characters and Classification Ill 



Systematic Position of the Example 112 



3. General Organisation 114 



SECTION IV 



Phylum Ccelenterata 128 



Class I. Hydrozoa '. 128 



1. Example of the Class — Obelia 128 



2. General Structure and Classification 140 



Systematic Position of the Example 142 



Additional Remarks 167 



Class II. Scyphozoa 168 



1. Example of the Class — Aurelia aurita 168 



2. General Structure and Classification 176 



Systematic Position of the Example 177 



Additional Remarks 184 



Class III. Actinozoa 185 



1. Example of the Class — Tealia crassicornis . . . . ' 185 



2. Distinctive Characters and Classification 193 



Systematic Position of the Example 196 



3. General Organisation . . . • 196 



Class IV. Ctenophora 211 



1. Example of the Class — Hormiphora plumosa 211 



2. Distinctive Characters and Classification 220 



Systematic Position of the Example 221 



3. General Organisation 222 



Appendix to Ctenophora— Ctenoplana and Codoplana . . . 225 



The Relationships of the Ccelenterata 226 



Appendix to the Ccelenterata — The Mesozoa . . . . . 230 



SECTION V 



Phylum Platyhelmixthes 235 



1. Examples of the Phylum . . 236 



i. Planaria or Dendrocodum ■ . 236 



ii. Fasciola hepaticci 240 



iii. Tamia solium 245 



