CONTENTS xv 



PHYLUM PLATYHELMINTHES continued. PAGE 



2. Distinctive Characters and Classification 248 



Systematic Position of the Examples f# 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 292 



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 Chcetosomatidce 313 



Echinoderidce 314 



,, Desmoscolecidce 314 



Affinities and Mutual Relationships of the Nemathelminthes . 315 



SECTION VII 



PHYLUM TROCHELMINTHES 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 Trochelminthes Dinophilea 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 . . . . . 340 

 Systematic Position of the Example 341 



3. General Organisation 341 



Class II. Phoronida 348 



Class III. Brachiopoda 353 



1. Example of the Class Magellania lenticularis .... 353 



2. Distinctive Characters and Classification 359 



Systematic Position of the Example 359 



3. General Organisation 360 



Mutual Relationships of the Classes of the Molluscoida . . 365 



