X CONTENTS 



CHAPTER IV. 

 THE LEECH. Hirudo medicinalis. 



PA.GE 



External characters Dissection Examination of transverse sec- 

 tions . 36 



CHAPTER V. 

 THE EARTHWORM. Lumbricus terrestris. 



External characters Dissection Examination of transverse sec- 

 tions . 55 



CHAPTER VI. 

 THE FRESHWATER MUSSEL. Anodonta cygnea. 



The shell Dissection of the mussel Examination of transverse 



sections . . . .75 



CHAPTER VII. 

 THE EDIBLE SNAIL. Helix pomatia. 



External characters Dissection of the snail 102 



CHAPTER VIII. 

 THE CRAYFISH. Astacus fluviatilis. 



External characters Dissection The arteries as seen in an 



injected specimen . . 124 



CHAPTER IX. 

 THE COCKROACH. Periplanria americana. 



Habits External characters Dissection 152 



