CONTENTS XI 

 CHAPTER XIV 



PAGE 



HYDRA AND ITS ALLIES . . . . . . . . . ' . 205 



APPENDICES : Key to the principal subdivisions of the Cnidaria 220 



Key to the families of the Hydroinedusae . . .. . 220 



CHAPTER XV 



THE PARAMECIUM AND ITS ALLIES . . .... . 222 



APPENDICES : Key to the four classes of Protozoa . . . 229 



Key to the subclasses and orders of Infusoria . . . 229 



CHAPTER XVI 



THE SMELT AND ITS ALLIES - . 230 



APPENDICES: Key to the principal orders of fishes . - . . 252 



Key to the six suborders of Teleostei 252 



CHAPTER XVII 



THE NEWT AND ITS ALLIES ........ 254 



APPENDICES : Key to the orders of Amphibia .... 266 



Key to the families of Urodela . . . . . . 266 



CHAPTER XVIII 



THE LIZARD AND ITS ALLIES . 268 



APPENDIX : Key to the four orders of Reptiles . * .,-" . . 280 



CHAPTER XIX 



THE ENGLISH SPARROW AND ITS ALLIES. . . . ^r . 281 



APPENDICES : Key to the orders of Birds . . . . " . . 314 



Key to the families of Passeres of northern United States . 315 



CHAPTER XX 



THE MOUSE AND ITS ALLIES ... ... . 318 



APPENDIX: Key to the orders of Mammalia "... . 331 



CHAPTER XXI 



THE DEVELOPMENT OF THE FROG'S EGG 332 



