xvi CONTENTS 



Page 



CHAPTER XXVII 



Hydra 136 



External features — Internal structure — Nematocysts — Neuromuscular 

 mechanism— Metabolism — Behavior — Reproduction — Symbiosis — Regen- 

 eration. 



CHAPTER XXVIII 



COELENTERATES IN GENERAL 1" 



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

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

 esis — Corals — Distribution and economic importance. 



CHAPTER XXIX 



Phylum Ctenophora 1^" 



Structure — Advances in body plan — Activities. 



CHAPTER XXX 



Fresh-water Planarian 1^9 



S t ru c t u r e— I n t e r n al structure — Metabolism — Reproduction— Behavior- 

 Regeneration. 



CHAPTER XXXI 



Phylum Platyhelminthes 166 



Classificatio n—Turbellaria—Trematoda—Cestoda— Metabolism— Repro- 

 duction — Occurrence and economic importance. 



CHAPTER XXXII 



Parasitism 1'^ 



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 178 



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 186 



Phylum Nemertinea — Phylum Chaetognatha — Phylum Rotifera — Phylum 

 Bryozoa — Phylum Brachiopoda. 



CHAPTER XXXV 



Starfish 1" 



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

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

 Reproduction — Regeneration and autotomy — Economic importance. 



CHAPTER XXXVI 



Phylum Echinodermata 203 



Retrogression — Specializations — Classification — Asteroidea — Ophiuroidea — 

 Echinoidea — Holothurioidea — Crinoidea — Reproduction — Behavior — Color 

 — Occurrence and economic importance. 



