CONTENTS xiii 



Page 



CHAPTER XXXVI 



Phylum Echinodermata 200 



Retrogression — Specializations — Classification — Asteroidea — Ophiuroidea — 

 Echinoidea — Holothurioidea— Crinoidea — Reproduction — Behavior — Color 

 — Occurrence and economic importance. 



CHAPTER XXXVII 



Fresh-water Mussel 208 



External appearance — Shell — Internal anatomy — Body mass and foot — 

 Mantle — Gills — Digestive system and metabolism — Circulatory system — 

 Excretory system — Musculature — Nervous system — Behavior — Reproduc- 

 tion — Other fresh-water mussels. 



CHAPTER XXXVIII 



MoLLUsKS IN General 217 



Classification — Amphineura — Gastropoda — Scaphopoda — P e 1 e c y p o d a — 

 Cephalopoda — Metabolism — Behavior — Reproduction and regeneration — 

 Economic importance. 



CHAPTER XXXIX 



Earthworm 229 



External characteristics — Internal structure — Alimentary canal and metabo- 

 lism — Circulatory system — Excretory system — Musculature and locomotion 

 — Nervous system — Behavior — Reproductive system and reproduction — 

 Regeneration — Economic importance. 



CHAPTER XL 



Reflex Action 238 



Nervous functions — Reflex acts — Anterior ganglia. 



CHAPTER XLI 



Annelids in General.- 241 



Classification — Archiannelida — Chaetopoda — H i r u d i n e a — G e p h y r e a — 

 Metabolism — Behavior — Reproduction — Occurrence and economic impor- 

 tance. 



CHAPTER XLII . 



Crayfish 250 



External characteristics — Internal structure — Eyes and vision — Statocyst — 

 Feeding habits — Behavior — Reproduction — Regeneration and autotomy — 

 Economic importance. 



CHAPTER XLIII 



Crustacea 260 



Malacostraca — Entomostraca — Behavior — Reproduction — Economic impor- 

 tance — Biogenesis. 



CHAPTER XLIV 



Onychophora and Myriapoda 268 



Onychophora — Myriapoda — Centipedes — Millipedes — R eproduction in 

 myriapods. 



