674 



VERMES— CLASS ANNELIDA. 



of the relatively poor development of the armature of bristles as compared 

 with the Polychasta. In other respects they are less highly organised, as is 

 shown by the absence of tentacles and gills and teeth, and by the fact that 

 the sexes are united in one individual. The best-known members of this 

 order are the familiar earth-worms, belonging to the families Lumbricidce, 

 etc. Most people are probably of opinion that but one species of this animal 

 occurs in Great Britain; but, as a matter of fact, there are about twenty 

 belonging to three distinct genera. Another popular belief connected with 

 them is, that if a couple of specimens be cut in two, and the head end 

 of one be applied to the tail end of the other, the two parts will grow 

 together and form a complete individual. In fact, the curious swelling 

 which may be observed in the fore part of the body of a full-grown worm is 

 often regarded as the point of union of two such separate pieces. As a 

 matter of fact, this swelling, called the clitellum or cingulum, is an organ 

 used in the formation of the cocoons in which the eggs are laid. 



Although occasionally seen on the surface of the ground during the day- 

 time. Earth-worms are for the most part strictly nocturnal and subterranean, 

 burrowing into the soil in all directions, and devouring any animal or 

 vegetable refuse it may contain. In connection with food they swallow 

 large quantities of earth, and when this has passed through their bodies, it 

 is voided at the surface of the ground, forming the so-called vegetable mould. 

 During spells of dry weather they bury themselves deep in the earth in 

 search of moisture, without which life is an impossibility ; and in the 

 winter months they descend to the lower layers of the soil so as to be out 

 of reach of the frost. These animals are subjected to ruthless persecution 

 at the hands of farmers and gardeners on account of their propensity for 

 pulling shoots of young corn and blades of grass beneath 

 the surface. But it is doubtful if the harm done in 

 this respect is not more than counteracted by the 

 benefit that plants derive from the ceaseless tunnelling 

 of the soil, the loosening of its particles, and the 

 porterage of the lower layers to the surface, to be 

 deposited as castings. In fact, so extensively is this 

 work carried on by earth worms, that Mr. Darwin has 

 compared their action to that of a plough, and adds 

 that it is doubtful whether many other animals have 

 played so important a part in the history of the world. 

 Earth-worms are found in all parts of the world in 

 spots suitable for their existence, and in some countries 

 they reach an enormous length as compared with the 

 common species with which we are familiar. In South 

 Africa, for instance, there is a species called Microchata 

 Sappi, which attains a length of about five feet. It is, 

 however, by no means frequently seen, rarely appear- 

 — "yS^fy^/Z^ — ^"^ °" ^^^ surface, and then only after heavy rains. 

 />Xi4i?^5'^^. Other worms, however, besides the earth-worms, 



belong to the Oligochreta. Many representatives of 

 this group live in fresh water streams and ditches, 

 as well as in the sea. For example, the common Tuhifex 

 rnndonun, a long, slender, reddish worm, may be found 

 in quantities in the muddy bottom of ponds, where it 

 constructs long tubular burrows. When undisturbed it has the peculiar 



Fig. 4.— Snouteb Nais 

 {Nais proboscidea). 



