xv i CONTENTS 



SECTION IX 



PAGE 



PHYLUM ECHINODERMATA , 368 



1. Example of the Asteroidea Asterias rubens or Anthenea flavescens 368 



2. Example of the Echinoidea Strongylocentrotus or Echinus . . 386 



3. Example of the Holothuroidea Cucumaria or Colochirus . . 393 



4. The Crinoidea Antedon rosacea 396 



5. Distinctive Characters and Classification 401 



Systematic Position of the Examples 405 



6. General Organisation 406 



SECTION X 



PHYLUM ANNULATA 429 



Class I. Chaetopoda 429 



1. Examples of the Class 430 



i. Nereis dumerilii 430 



ii. Lumbricus 443 



2. Distinctive Characters and Classification 454 



Systematic Position of the Examples 455 



3. General Organisation 457 



Appendix I. to the Chaetopoda Class Myzostomida . . . .477 



Appendix II. to the Chaetopoda Class Echiurida . . . . 479 



Class II. Sipunculoidea 484 



1. Example of the Class Sipunculus nudus 484 



2. Distinctive Characters 488 



3. General Organisation 488 



Class III. Archi-annelida 491 



Class IV. Hirudinea 494 



1. Example of the Class Hirudo medicinalis and H. australis . 494 



2. Distinctive Characters and Classification 503 



Systematic Position of the Example. 504 



3. General Organisation 505 



General Remarks on the Annulata 510 



SECTION XI 



PHYLUM ARTHROPODA 514 



Class I. Crustacea 514 



1. Examples of the Class 514 



i. Apus or Lepidurus ......... 514 



ii. Astacus fluviatilis . . . . . . . . .527 



2. Distinctive Characters and Classification 548 



Systematic Position of the Examples 555 



3. General Organisation 556 



Affinities and Mutual Relationships 587 



Appendix to Crustacea Class Trilobita 589 



Class II. Onychophora . 591 



