CONTENTS xv 



PHYLUM PLATYHELMINTHES continued. PAGE 



2. Distinctive Characters and Classification . .... 248 

 Systematic Position of the Examples .... . 249 



3. General Organisation . . 250 



4. Distribution, Mode of Occurrence, and Mutual Relationships . . 279 

 Appendix to Platyhelminthes Class Nemertinea . . 284 

 Distinctive Characters and Classification 290 



SECTION VI 



PHYLUM NEMATHELMINTHES . 2 ( .i2 



Class I. Nematoda . 292 



1. Example of the Class Ascaris lumbricoides 292 



2. Distinctive Characters and Classification . . . . 298 

 Systematic Position of the Example . . . . . 299 



3. General Organisation . . ... 299 

 Class II. Acanthocephala . . 307 

 Class III. Chaetognatha .310 



Appendix to Nemathelminthes ... .313 



Family ChcetosomatidcB ... . . . . 313 



,, Echinoderidce 314 



,, Desmoscolecidce 314 



Affinities and Mutual Relationships of the Nemathelminthes . 315 



SECTION VII 



PHYLUM TKOCHELMINTHES . . 316 



Class I. Rotifera . . . .317 



1. Example of the Class Brachionus rubens .... 317 



2. Distinctive Characters and Classification 321 



Systematic Position of the Example. . .... 323 



3. General Organisation .... .... 323 



Class II. Gastrotricha . .... ... 328 



Appendix to Trochelininthes DinophUia and Histriobdellea . 330 



SECTION VIII 



PHYLUM MOLLUSCOIDA . . 333 



Class I. Polyzoa . . . 333 



1. Example of the Class Bugula avicularia ... . 334 



2. Distinctive Characters and Classification .'540 



Systematic Position of the Example. . . . . . .341 



3. General Organisation . . 341 



Class II. Phoronida ... . 348 



Class III. Brachiopoda .353 



1. Example of the Class Mag ellania lenticular is . . . 353 



2. Distinctive Characters and Classification 359 



Systematic Position of the Example. ... . 359 



3. General Organisation 300 



Mutual Relationships of the Classes of the Molluscoida . 365 



