XIV CONTENTS. 



CHAPTEE IV. 



The Lkech. Hirudo med/icmaUs. 



PAGE 



External characters — Dissection — Examination of transverse sec- 

 tions 39 



CHAPTER V. 



The Earthworm. Lumbricua herculeus. 



External characters — Dissection — Examination of transverse sec- 

 tions 59 



CHAPTER VI. 



The FRESHvyATER Mussel. Anodonta cygnea. 



The shell — Dissection of the mussel — Examination of transverse 



sections .81 



CHAPTEE VII. 



The Edible Snail. Helix pomatia. 



External characters — Dissection of the snail 109 



CHAPTER VIII. 



The Crayfish. Astacus fluviatilis. 



Externalcharacters— Dissection— The arteries as seen in an in- 

 jected specimen -^go 



CHAPTER IX. 



The Cockroach. Periplaneta Americcma. 



Habits — External characters — Dissection .... iri 



