CONTENTS xv 



1'Al.K 



Phylum Piati hii.mintuks 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 . 2'.»r> 



SECTION VI 



Phylum Nemathelminthes' 297 



Class I. Nematoda 297 



1. Example of the Class — Ascaris lumbricvides 297 



2. Distinctive Characters and Classification 303 



Systematic Position of the Example 304 



3. General Organisation 305 



Class II. Acanthocephala 312 



Class III. Chsetognatha 316 



Appendix to Nemathelminthes 319 



Family Chatoso-micUe 319 



,, Echinoderidce 311) 



,, Desmoscolecidce 320 



Affinities and Mutual Relationships of the Nemathelminthes . 320 



SECTION VII 



Phylum Tkochelminthes 322 



(lass 1. Rotifera - 323 



1. Example of the Class — Brachionu* 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 — Bxigula 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 880 



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 



