CONTENTS 



CHAPTER XVI. 



The Platyhelmia ; Distomum hepaticum ; External Feature 

 Alimentary Tract ; Excretory System ; Reproductive System ; 

 Nervous System ; Histology ; Parasitism ; Development ; 

 The Miracidium Larva ; Sporocyst ; Redia ; Cercaria ; 

 Alternation of Generations ; Coelom . . . 1-16 



CHAPTER XVII. 



The Common Earthworm ; Lumbricus herculeus ; External 

 Features ; Metamerism ; Alimentary Tract ; Coelom ; Ex- 

 cretory System ; Nervous System ; Blood- vascular System ; 

 Histology ....... 17-32 



CHAPTER XVIII. 



The Earthworm ; Reproductive Organs ; The Ova ; Segmentation 

 and Formation of Blastula ; Gastrulation ; Mesoblast Bands ; 

 Mesoblastic Somites ; Neuroblasts and Nephroblasts ; For- 

 mation of Nephridia ...... 33-44 



CHAPTER XIX. 



The Annelida ; Archiannelida ; Polygordius ; The Trochosphere 

 Larva ; The Chaetopoda ; Polychseta ; Hirudinea ; Echiu- 

 roidea ; Metameric Segmentation .... 45-52 



CHAPTER XX. 



The Mollusca ; Anodonta cygnea ; The Shell ; Muscular Impres- 

 sions ; Mantle ; Mantle Cavity ; Foot ; Visceral Hump ; Ali- 

 mentary Tract ; Gills ; Blood-vascular System ; Pericardial 

 Cavity ; Excretory Organs ; Nervous System ; Reproductive 

 System ; The Glochidium Larva ; Dreissensia polymorpha ; 

 Veliger Larvae ; Migrations of Lamellibranchs . 53-68 



CHAPTER XXI. 



The Gastropoda ; Helix pomatia and Helix aspersa ; The Shell ; 

 The External Features ; The Pulmonary Cavity j The 



