xvi TABLE OF CONTENTS 



LESSON XXI. 



HYDRA 



PAGE 

 2l8 



LESSON XXIL 



HYDROID POLYPES ^34 



BOUGAINVILLEA, &C 234 



DIPHYES ^48 



PORPITA ^49 



LESSON XXIIL 



SPERMATOGENESIS AND OOGENESIS . . • 253 



THE MATURATION AND IMPREGNATION OF THE OVUM .... 258 

 THE CONNECTION BETWEEN UNICELLULAR AJ<D DIPLOBLASTIC 

 ANIMALS 



POLYGORDIUS 



LESSON XXIV. 



268 



1 



v/ 



LESSON XXV. 

 POLYGORDIUS {continued) ^9° 



LESSON XXVI. 



THE CHIEF DIVISIONS OF THE ANIMAL KINGDOM 304 



THE STARFISH ^ 



LESSON XXVII.. 



318 



THE CRAYFISH 



THE FRESH-WATER MUSSEL 



LESSON XXVIII. 



348 



