226 



NATURAL HISTORY. 



a calcareous matter. This gullet widens into a sort of crop, which terminates in a thick and muscular 

 gizzard. Then follows a single tube the intestine which is turned in, as it were, along its back, 

 so that there is a longitudinal projection into the intestinal canal. The exci'etory or segmental 

 organs are tubes which are much convoluted, and one is situated on each side of every segment 

 except the first. Externally, it opens by a minute pore placed close to a pair of bristles or setae ; and 

 internally it communicates with the perivisceral cavity by a wide, funnel-shaped ciliated aperture. 



Each segment of the body has four double rows of minute setae on it, which project slightly 

 beyond the integument, and pass inwards into the tissues. A series of small apertures, or pores, one 

 for each segment except the first, is on the back, in the median line, and they lead inwards to 

 the perivisceral cavity ; and upon the opposite side of the body are eight apertures for the reproduc- 

 tive organs. When an Earth Worm is in good health and clean, its thin, transparent, but dense 

 outside skin shows a play of colours. Within this layer is a connective tissue with the meshes filled 

 with a gelatinous substance, and still within is a thick layer of circular muscular bands, with pigment 

 granules. A longitudinal layer of muscular fibres is internal to all the rest. So the outside of the 

 Worm is muscular and membranous, and contains many cells for the secretion of mucus outside, and 

 passages into the inside. Within are the viscera and the perivisceral cavity, and this is subdivided 

 by a tissue which passes inwards from the divisions between each pair of seg- 

 ments. Yet there is communication between each subdivision, and also between 

 it and the outside, through the segmental organs. The short spinets, or curved 

 setae, project farther into the interior of the body than externally. The ends 

 of each pair are close, but their origins within the body are wider apart ; each 

 is enclosed in a sac in which it is developed, and to which the muscles by 

 which it is protruded are attached. There are eight setae to a segment ; one pair 

 is not far from the middle line below, and the other pair are farther out on 

 either side. 



There is a coloiirless fluid with corpuscles in the perivisceral cavity, and the 

 B deep-red fluid already mentioned is found in a system of pseudo-haemal vessels. 

 These are longitudinal and transverse canals and branches, ramifying in all parts 

 of the body except the outside skin. In the seven front segments the longitudi- 

 nal vessels form a network, and behind it cross vessels are greatly developed, 

 I and form five to eight pairs of false hearts. They contract from the back towards 

 the under side. 

 The Earth Worm is very widely distributed ; and some of the species, for 

 there are many, are found on continental and oceanic islands, yet they neither 

 swim nor like salt. They are all nocturnal in their habits, and swallow earth, 

 and digest any organic matters which may be in it, casting forth the residue 

 in the form of cylindrical twists of sand or mud. Charles Darwin has 

 shown that they are the great producers of good soil, and hence the term vegetable mould 

 should rather be animal or worm mould. The Worm should therefore be cultivated rather than 

 destroyed, and the only harm it can do is when it lives in the same pot as a flower, for then 

 it abstracts the organic part of the mould which would be of use to the vegetable. Formerly 

 Worms were much used in medicine. The Earth Worm lays its eggs in capsules at some depth 

 in the soil during the spring, and they hatch in the summer, and the young are about an 

 inch in length, and have no clitellus. Like many other Vermes, the Earth Worm has the power 

 of reproducing lost parts, and of healing and growing when cut in half. Anglers use the 

 common Earth Worm for Eels and Perch, but another species, the Brandling (Lumbricus 

 foetidus), is the best for Trout. This is a reddish-brown Worm with alternate yellow and 

 brown segments, and it has a tapering tail, and exudes a yellow pungent fluid when touched. 

 A huge Worm occurs in Ceylon, called Megascolex cceruleus, and it is sometimes forty inches 

 long, and is as thick as a finger. Its segments are surrounded by a complete circle of seta^ 

 Dr. Baird described a species of this genus which had been found in a hot-bed in a garden in Wales, 

 but probably it had been introduced accidentally. 



There are many species of Lumbricus in England. In one, the front of the body is different 



SF1XE (A) AND SPIXET 

 (B) OF LUMBRICUS 

 TERRESTRIS. 



