CONTENTS xv 



PAGE 



PHYLUM PLATYHELMINTHES continued. 



2. Distinctive Characters and Classification 251 



Systematic Position of the Examples 253 



.">. General Organisation 254 



4. Distribution, Mode of Occurrence, and Mutual Relationships . 283 



Appendix to Platyhelminthes Class Nemertinea . . . 288 



Distinctive Characters and Classification 295 



SECTION VI 



PHYLUM NEMATHELMINTHES 297 



Class I. Nematoda ... 297 



1. Example of the Class Ascaris lumbricoides 297 



2. Distinctive Characters and Classification ..... 303 

 Systematic Position of the Example 304 



3. General Organisation 305 



Class II. Acanthocephala . . 312 



Class III. Chatognatha .... 316 



Appendix to Nemathelminthes 319 



Family Chcetosomidce 319 



,, Echinoderidce 319 



,, Desmoscolecidce 320 



Affinities and Mutual Relationships of the Nemathelminthes . 320 



SECTION VII 



PHYLUM TKOCHELMINTHES 322 



Class I. Rotifera . . . 323 



1. Example of the Class Brachionus rubens 323 



2. Distinctive Characters and Classification 327 



Systematic Position of the Example 329 



3. General Organisation 330 



Class II. Gastrotricha , 335 



Appendix to Trochelminthes Dinophttea and Histriobdellea . 336 



SECTION VIII 



PHYLUM MOLLUSCOIDA 340 



Class I. Polyzoa . . ... .340 



1. Example of the Class Bugida avicularia 341 



2. Distinctive Characters and Classification . . . 347 

 Systematic Position of the Example 348 



3. General Organisation 348 



Class II. Phoronida . . 355 



Class III. Brachiopoda 360 



1. Example of the Class Magellania lenticultirix . . . 360 



2. Distinctive Characters and Classification . . . 366 

 Systematic Position of the Example 367 



3. General Organisation 367 



Mutual Relationships of the Classes of the Molluscoida . . 372 



