CONTENTS ix 



THREAD -WO RMS (NEMATHELMIA) 



Page 



Structure of a Round- Worm (Ascaris). Vinegar-Eel (Anguillula), Gordian- 



Worm (Gordius), Thorn-headed Worm (Echinorhynchus) - - 447 



CHAPTER XI 

 STRUCTURE AND CLASSIFICATION OF ECHINODERMS 



(ECHINODERMATA) 



Structure of the Common Star-Fish (Uraster rubens) - 450 



Class i. STAR-FISHES (Asteroidea) 454 



Class 2. BRITTLE-STARS (Ophiuroidea) 455 



Class 3. SEA-URCHINS (Echinoidea) - 45 6 



Class 4. SEA-LILIES AND FEATHER-STARS (Crinoidea) 459 



Class 5. SEA-CUCUMBERS (Holothuroidea) 462 



CHAPTER XII 



STRUCTURE AND CLASSIFICATION OF ZOOPHYTES (CCELENTERATA), 

 SPONGES (PORIFERA), AND ANIMALCULES (PROTOZOA) 



ZOOPHYTES (CCELENTERATA) 



Structure and Development of the Fresh-water Polype (Hydra), taken as a 



Type. Comparison with higher forms. Cells and tissues - 465 



Class i. SEA-FLOWERS (Actinozoa or Anthozoa) 473 



Structure of the Beadlet (Actinia mesembryanthemum), taken as a Type - 473 



Order i. SIX-RAYED SEA-FLOWERS (Hexactinia) - 474 



(i) Sea-Anemones (2) Corals. 



Order 2. EIGHT-RAYED SEA-FLOWERS (Octactinia) 476 



Structure of the Dead-Man's Fingers (Alcyonium digitatum), taken as a 

 Type. Organ- Pipe Coral (Tubipora musica), Red Coral (Corallium 

 rubrum), Sea-Pens and Sea-Mats. 



Class 2. HYDROIDS (Hydrozoa) 4?8 



Structure and Development of Obelia, taken as a Type- 478 



Order i. BUDDING HYDROIDS (Hydromedusae) 480 



(i) Hydroid Zoophytes and "Naked-eyed" Medusas (2) Compound Jelly- 



Fish (Siphonophora). 



Order 2. SPLITTING HYDROIDS (Scyphomedusae) - - 481 



Class 3. COMB JELLY-FISH (Ctenophora) 483 



Structure of Cydippe. Venus's Girdle, Beroe, Creeping Ctenophores. 



SPONGES (PORIFERA) 



Structure of a Simple Sponge - - - 484 



(i) Calcareous Sponges (2) Siliceous Sponges. 



ANIMALCULES (PROTOZOA) 



Protoplasm. Description of the Proteus Animalcule (Amoeba), taken as a 



Type. Comparison of Protozoa and higher forms (Metazoa) - 484 



