CONTENTS. ix 



_ I'AGE 



CHAPTER IX. 



PORIFF.RA OR SpONGES . . . 1 14 



CHAPTER X. 



CCELENTERATA OR STINGING ANIMALS. 



General Characters— General Classification — Survey of Types : 

 Hydra, Medusoids, Aiirelia, Sea-Anemone — Hydrozoa — 

 Scyphozoa — Ctenophora — General Scheme of Ccelenterata, 121 



CHAPTER XI. 



Worms. 



Classification — Turbellaria — Trematoda — Cestoda — Nemertina 

 — Nematoda — Acanthocephala — Chsetopoda — Type : Earth- 

 worm — Discophora — Type : Leech — Chsetognatha — Rota- 

 toria — Sipunculoidea — Phoronidea — Polyzoa or Bryozoa — 

 Brachiopoda, . .... 148 



CHAPTER XII. 



ECHINODERMATA. 



General Characters — Asteroidea — Ophiuroidea — Echinoidea — 

 Holothuroidea — Crinoidea — Blastoidea — Cystoidea — De- 

 velopment of Echinoderms — Some contrasts between the 

 Classes, . . .... 201 



CHAPTER XIII. 



Arthropoda. 



General Characters — Crustacea — Type : Crayfish — Protracheata 



— Myriopoda — Insecta — Type : Cockroach — Arachnoidea, . ,224 



