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it is obvious that their work is, and has been, of considerable 

 importance. They are largely nocturnal in habit, and then 

 may be seen on the surface. Pairing, however, takes place 

 almost at any time of the year, and the worms of adjoining 

 burrows may then be seen attached by the secretion of the 

 clitellum and the capsulogenous glands. The hinder part 

 of the body remains in the burrow, and when disturbed the 

 worms quit their hold of one another and retreat instantly. 

 Worms form the food of many birds and mammals, and are 

 liable to gregarine and other parasites. For further interest- 

 ing facts relating to the natural history of earthworms consult 

 Darwin's ' Vegetable Mould and Earthworms.' 



EXTERNAL MORPHOLOGY. The general appearance is 

 familiar. The worm is cylindrical in shape, and posteriorly it is 

 somewhat flattened dorso-ventrally. It is made up of a large 

 number of rings or segments delimited by slight grooves. The 

 segments are capable of extension and contraction by the muscles 

 underneath the skin, and the movements are assisted by the 

 chitinous hooks (chaetae or setae), of which there are eight 

 on each segment except the first and the last. The colour is 

 variable, but the dorsal side is darker, brown to purple, and the 

 dorsal blood-vessel may usually be seen through the thin skin 

 as a dark red line. The saddle, or clitellum, is a conspicuous 

 glandular swelling extending between segments 31 and 37, but 

 varying according to circumstances of maturity and in different 

 species. The capsulogenous glands are similar paired ventral 

 enlargements of the segments, 9, 10, 11, involving slightly also 

 8 and 12. Some of the openings may be distinguished easily, 

 others with difficulty. The mouth may be seen on the lower 

 aspect of the first segment, and the anus on the last segment. 

 The part of the first segment in front of the mouth is sensory, 

 and is called the prostomium. The fifteenth segment is usually 

 plainly defined by the swollen lips of the opening of the vas 

 deferens on each side. The fourteenth segment bears the 

 openings of the oviducts, for the earthworm is hermaphrodite, 

 but they are minute. Two other openings connected with 

 the reproductive organs are to be found on each side between 

 segments 9 and 10 and between 10 and 11 ; these lead into 

 sacs called the spermathecae, of which there are two pairs. 



