xii CONTENTS 



Page 

 ton — Histology — Metabolism — Behavior — Reproduction — Uses of sponges 

 — Cultivation of sponges — Relations to other animals. 



CHAPTER XXVII 



Hydra I34 



External features — Internal structure — Nematocysts — Neuromuscular 

 mechanism — Metabolism — Behavior — Reproduction — Symbiosis — Regener- 

 ation. 



CHAPTER XXVIII 



COELENTERATES IN GENERAL 142 



Polyps and Medusae — Classification — Hydrozoa — Scyphozoa — Anthozoa — 

 Color — Polymorphism — Metabolism — Behavior — Reproduction — Metagen- 

 esis — Corals — Distribution and economic importance. 



CHAPTER XXIX 



Phylum Ctenophora 154 



Structure — Advances in body plan — Activities. 



CHAPTER XXX 



Fresh-water Planarian 157 



Structure — Internal structure — Metabolism — Reproduction — Behavior — 

 Regeneration. 



CHAPTER XXXI 



Phylum Platyhelminthes 164 



Classification — Turbellaria — Trematoda — Cestoda — Metabolism — R e p r o - 

 duction — Occurrence and economic importance. 



CHAPTER XXXII 



Parasitism ....<• 1 70 



Structure of parasites — Sheep liver fluke — Life history of the sheep liver 

 fluke — Life history of a tapeworm — Behavior of parasites — Practical 

 aspects. 



CHAPTER XXXIII 



Phylum Nemathelminthes 175 



Structure of an ascaris — Characteristics and advances — Classification — 

 Free-living nematodes — Metabolism — Reproduction — Life history of the 

 pig ascaris — American hookworm — Trichinella — Filaria — Hairworms — 

 Spiny-headed worms — Economic importance. 



CHAPTER XXXIV 



Other Unsegmented Worms 183 



Phylum Nemertinea — Phylum Chaetognatha — Phylum Rotifera— Phylum 

 Bryozoa — Phylum Brachiopoda. 



CHAPTER XXXV 



Starfish 191 



External appearance — Skeleton and musculature — Water-vascular system — 

 Internal organs — Feeding and metabolism — Nervous system and behavior — 

 Reproduction — Regeneration and autotomy — Economic importance. 



