xiv CONTENTS. 



IV. 



COMMON SNAIL. 



Specific characters of Helix aspersa and fT. hortensis Habitat 

 General characters Shell or exoskeleton Digestive system Pulmo- 

 nary sac and excretory organ Heart, compared with that of Crayfish 

 Circulatory system Nervous system and sense organs Reproductive 

 system Development of Pond Snail (Lymnaus stagnate) Polar 

 bodies Laboratory work pp. 272 304. 



V. 



FRESH-WATER MUSSEL. 



Habitat General characters Branchiae and alimentary canal, in 

 relation to the branchial chambers and the exterior Circulatory system 

 and heart Excretory organs Digestive gland and glycogenous tissues 

 Nervous system and sense organs Reproductive organs Develop- 

 ment Laboratory work. ...... pp. 305 341. 



VI. 



FRESH-WATER POLYPES. 



Habitat and movements Mode of feeding Reproduction and repro- 

 ductive organs Histological structure Specific characters of Hydra 

 fusca and H. viridis Symbiosis probably exemplified by Comparison 

 with Amceba Neurosensiferous apparatus Comparison with develop- 

 ment of higher animals Laboratory work. . . pp. 342 358. 



VII. 



BELL- ANIMALCULE. 



Infusoria, compared with other animals BELL-ANIMALCULE 

 Habitat and movements Histological structure Physiology Green 

 varieties and chlorophyll Reproduction Encystation Infusoria asso- 

 ciated with Frog Laboratory work pp. 359 368. 



