78 CONTENTS. 



Page. 



Part 2. Life history and propagation of fresh-water mussels 135 



Introduction 135 



Historical note 136 



Age at which breeding begins .' 137 



Ovulation and fertilization 138 



Brood pouches or marsupia 138 



Seasons of deposition of eggs 140 



Seasons of incubation of eggs 140 



Glochidium 143 



Stage of parasitism ., 148 



Hosts of fresh- water mussels 151 



Parasitism and immunity' 155 



Metamorphosis without parasitism 156 



Juvenile stage 137 



Artificial propagation 160 



Principle of operation i . ».. 160 



Methods 160 



Mussel culture 163 



Part 3. Structure of fresh-water mussels 167 



Introduction 167 



The shell 168 



External features 168 



Internal features 169 



Biversity in form 170 



The soft body 171 



Form and functions of the mantle 171 



Other conspicuous organs 172 



Internal structure 173 



Structure and functions of the gills 174 



Bibliography 177 



