SOILS AND THEIR COMPOSITION 163 



with them large quantities of soil, and in any case the 

 value of their services is out of all proportion to the small 

 amount of damage, if any, that can be laid to their charge. 



The Common Earthworm {Lumbricus terrestris) belongs 

 to the first class of articulated animals, the AnneHdes, 

 which are the only invertebrates that have red blood. 

 Most of them live in the water, the Earthworm itself 

 being an exception to the rule. The Annehdes are 

 divided into three orders, (1) The Mud- worms and Sea- 

 worms, (2) The Sand-worms and Sea-mice, (3) The Earth- 

 worms and Leeches. 



Worms have neither eyes, gills, tentacles nor teeth. 

 The digestive process is carried on by means of a gizzard, 

 and they swallow for this purpose large quantities of 

 earth and grit along with the odd leaves, roots, fibre, 

 decayed woods and animal matter upon which they 

 subsist. When f ullgr^wn the common earthworm attains 

 a length of nearly a foot. The breeding season is in the 

 month of June and propagation is by means of eggs, 

 which are sometimes hatched within the body of the 

 parent, and sometimes laid in their burrows where the 

 young ones subsequently appear. A drawing is shown 

 of both the adult and eggs, with young therein, the latter 

 considerably enlarged. Figure (e) shows the head of a 

 worm, the shape of the mouth and also the bristles on 

 the segments, directed backwards, a contrivance by 

 which worms force themselves along their burrows and 

 through the soil. (See Plate 40.) 



Worms are nocturnal in habits, and lie as a rule close 

 to the mouth of their burrows. As stated, they have 

 no eyes, but they nevertheless seem able to distinguish 

 the difference between fight and darkness. Darwin 

 considered them to be completely deaf. There is nothing 

 in their anatomy to represent auditory powers, it is 

 true, but there is stiU a possibifity that this may be 

 made up for by some development of instinct as yet 

 unexplained. 



