Vlll 



CONTENTS. 



Chapter XX1IT. 



XXIV. 



XXV. 



XXVI. 



,, XXVII. 



,, xxvur. 



XXTK. 

 XXX. 



XXXI. 

 ,, XXXII. 

 XXXIII. 

 XXXIV. 



XXXV. 



APPENDIX 



PA RT IV. IN V ERTEBRATA. 



TAUK 



The Crayfish .. .. .. ..301 



The Fresh- Water Mussel .. .. 324 



The Earthworm . . . . . . 336 



External Characters of Nereis . . . . 340 



The Liver-Fluke .. .. ..355 



The Pork Tape-Worm . . . . . . 3GG 



The Fresh Water Polyp .. .. .. 37(> 



Obelia Geaiculata . . . . . . 387 



The Slipper- Animalcule . . . . . . 309 



Euglena . . . . . . . . 405 



Monocystis and Coccidium . . . . 413 



The Mala ri.il Parasite .. .. .. 423 



Diagnostic Characters of the Principal Divi- 

 sions of the Animal Kingdom . . . . 428 



Questions on the Invertebrata .. .. 455 



. 4f>9- 



