XIV CONTENTS. 



IV. 



Common Snail. 



Specific charactei-s of Helix aspersa and //. hortcnsis — Ilal^'tat — 

 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 {Lytnviins stagnalis) — 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 //. z'/r/t//j— Comparison with green-plant and Amoeba — 

 Neurosensiferous apparatus — Comparison with development 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. 



