CONTENTS. 



LETTER I. 

 Intboductoey page 1 



LETTER n. 



The Class " Vermes " and its subdivision into Orders. — 

 Lumhricm terrestris, the common Earthworm. — Its Form. 

 — Members of Locomotion. — Mouth. — Aliment. — Nature 

 of Worm-Castings. — ^Digestive Organs. — Circulating Ap- 

 paratus. — ^Nervous System 8 



LETTER ni. 



Mode of Reproduction in the Earthworm. — ^Its Habits. — 

 Dwelling. — Uses in the Formation of the Surface SoU.— 

 Conclusion 17 



LETTER IV. 



Cuvier's Classification of Annelides and Insects. — Guides to 

 a Systematic Arrangement of Animals. — AflSnities be- 

 tween the Worm and Fly. — Classification of Insecta, and 

 the position of the House-fly {Musca domesticd) in the 

 Class. — General Consideration of the Fly's Form and 

 Structure 26 



LETTER V. 



The Antennae or Feelers of the Fly ; their Structure ; and 

 various theories regarding their Functions. — The Eyes, 

 compound and simple ; their Structm-e and Uses 34 



