CONTENTS xiii 



CHAPTER XIV. 



The Coelenterata, Hydra fusca and Hydra viridis. Structure of 

 Hydra. Ectoderm, Mesogloea, and Endoderm. Nemato- 

 cysts. Reproduction and Development of Hydra . . 250-269 



CHAPTER XV. 



Dbelia geniculata. Structure of the Colony. The Medusa, its 

 Structure and Development. Comparison of Medusa and 

 Polype. Sexual Development of Obelia. Theory of Indi- 

 viduality ....... 270-283 



CHAPTER XVI. 



Classification. Phylum, Class, Order, Family, Genus and 

 Species. System of Linnzeus. Genealogy of Animals. 

 Progress in Classification . , . . 284-287 



