CHAPTER I. 



EARTHWORMS AND LEECHES. 



EARTHWORMS occur commonly in nearly all parts of 

 England. Their body is roughly cylindrical, but tapers 

 towards each extremity. It is divided into a number of 

 similar rings or segments, about 140 180, by constricting 

 furrows. The surface is moist and iridescent ; this latter 

 property is an optical effect produced by the fine striations 

 with which the delicate cuticle is engraved, and is not due 

 to the presence of any pigments. Earthworms inhabit 

 burrows in the surface of the earth, and for the most part 

 limit their operations to the top 12 or 18 inches (i.e. in the 

 soil which is richest in decomposing vegetable and animal 

 substances and in which decomposition occurs most 

 rapidly), but during periods of prolonged drought or frost 

 they descend to greater depths and undergo aestivation or 

 hibernation, as the case may be, coiled up into a compact 

 spiral and lying in a small excavated chamber. This is 

 lined with small stones which prevent close contact with 

 the surrounding earth and so permit free respiration. 

 L. 1 



