CONTENTS xv 



PAGK 



PHYLUM PLATYHELMINTHES continued. 



2. Distinctive Characters and Classification 251 



Systematic Position of the Examples . . . . . . . 253 



3. 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. Chajtognatha 



Appendix to Nemathelminthes 319 



Family Chcetosomidw 319 



,, Echinoderidm 319 



,, Desmoscolecidie 320 



Affinities and Mutual Relationships of the Nemathelminthes . 320 



SECTION VII 



PHYLUM TROCHELMINTHES 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 Dinophilea and Histriobdellea . 336 



SECTION VIII 



PHYLUM MOLLUSCOIDA 340 



Class I. Polyzoa 340 



1. Example of the Class Bugida avicitiaria 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 lenticitlaris .... 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 



