xvi CONTENTS 



SECTION IX 



PACJE 



Phylum Echinodermata . 375 



1. Example of the Asteroidea — Asterias rubens or Anthenea Jtdvetcens. 375 



2. Example of the Echinoidea — Wrong i/locentrotus or Echinus . . 393 



3. Example of the Holothuroidea — Cucnmaria or Colochirus . . 401 



4. The Crinoidea — Antetkm rosacea . . 405 



5. Distinctive Characters and Classification .410 



Systematic Position of the Examples 414 



6. General Organisation 415 



SECTION X 



Phylum Annulata 439 



Class I. Chaetopoda 439 



1. Examples of the Class 440 



i. Nereis dumerilii 440 



ii. Lwnribricus 454 



2. Distinctive Characters and Classification 464 



Systematic Position of the Examples . . . . . . 460 



3. General Organisation 467 



Appendix to the Chaetopoda — Class Myzostomida .... 489 



( 'lass II. Gephyrea 491 



1. Example of the Class — Sipuncidus nudus 492 



2. Distinctive Characters and Classification . . . . 495 



3. General Organisation . . 496 



Class III. Archi-annelida 503 



Class IV. Hirudinea 506 



1. Example of the Class — Hirudo medicinalu and H. audraUs . 506 



2. Distinctive Characters and Classification 515 



Systematic Position of the Example ' ... 517 



3. General Organisation 517 



4. General Remarks on the Annulata 523 



SECTION XI 



Phylum Arthropoda 526 



Class I. Crustacea 526 



1. Examples of the Class 526 



i. Apus or Lepidurus 526 



ii. Astacus fiuviatilis 539 



2. Distinctive Characters and Classification 561 



Systematic Position of the Examples 569 



"3. General Organisation 570 



Affinities and Mutual Relationships 602 



Appendix to Crustacea — Class Trilobita 604 



Class II. Onychophora ; . .607 



Class III. Myriapoda 614 



1. Distinctive Characters and Classification . . . " . . 614 



2. General Organisation til5 



