CONTENTS. 



Page. 



Introduction i8i 



Reproductive organs 182 



Female 182 



Ovary 182 



Male 185 



Modified anal fin .' 185 



Mechanism controlling anal fin 185 



Testis 186 



Embryology 187 



Ovum 187 



Blastoderm 187 



Differentiation of the embryo 187 



Later development 188 



Summary 189 



179 



