THE TUBIFICID^E. 227 



from the hinder part, L. anatomicus ; one is greenish, and is found under stones in cattle fields, 

 L. viridis ; another is phosphorescent, and there is a pigmy form of the great Earth Worm. 



The second sub-order is that of the water- and mud-inhabiting Oligochseta the Oligochceta 

 limicola. There are four families of them, and that of the Naidae is the most important, Nais 

 proboscidea being the type. These Naidaa have a head distinct from the body, and the first three 

 or four segments have no bristles. The mouth is exactly terminal, and there is no overhanging lip 

 as in the Earth Worm. Their body is much flattened, and the bristles are comparatively long, 

 and there are two kinds of them on the segments, which are rather indistinct. The upper bristles 

 are seta?, and are collected in small bundles, and the lower are spinets, which are forked at the 

 tip ; and with their aid the Worms creep actively, and even swim. They live on small animals and 

 are oviparous. They are remarkable for their facility of multiplying by spontaneous division. 

 This has been noticed in the typical species, whose individuals are about half an inch long, and are 

 found about the roots of aquatic plants. Mr. Lewis noticed that the perfect Worm begins to grow a 

 second head near the extremity of the body, and then other segments are developed, the tail, or 

 final segment, being the identical tail of the mother, but pushed forward by the young segments, and 

 now belonging to the child, and only vicariously to the mother. In this state, he adds, we have 

 two Worms and one tail. In some other species the tail has finger-shaped processes which probably 

 act as respiratory organs. One genus, Aulophorus, secretes a tube, which it carries about, and 

 its upper bristles are hair-like, and the lower ones stiff. Some Naidse have eyes, as in the instance 

 of the type, but one species, which has finger-shaped projections (Protodigitata), has not any. The 

 genus Cluetogaster has a cylindrical body, truncated in front, without eyes ; and the mouth, which is 

 terminal, is barbed underneath on the first segment. The bristles are in a single row on either 

 side of the ventral aspect, but they are massed together in groups of four or five or more hooked 

 setaa. They reproduce principally by a process of gemmation or budding, and form chains of four, 

 eight, or sixteen individuals, and each has four segments including the head. 



The genus Lumbriculus, which has a contractile vascular space to each segment, and no vascular 

 network in the skin, has species living in fresh water, which are red or brown in colour, and have no 

 clitellus. 



The family Enchytraeidae may be typified by a Scottish species (E. vermicularis). This is a 

 white, indistinctly segmented Worm, with the thirty to seventy segments armed with short spinets 

 in four small fascicles or bundles. It lives in the soil under the bark of rotted trees or decaying 

 leaves. There is a small white spot near the first third of the body. If this little Worm, which 

 is found lying rolled up in a loose, spiral manner, be placed on one's hand, it wriggles much and soon 

 dies. It cannot live except in moist places. 



The family Tubificidae contains numerous genera, with four rows of recurved setae, which may 

 be simple or forked, and the species have contractile vascular canals, besides the dorsal vessel. The 

 reproductive organs are in the 9 11 segments. These Worms* live in water in cylindrical tubes 

 of mud on the bottoms of streams, and their mouth segments are united, and often lengthened, and 

 their skin is transparent and appears of a deep red colour in the water; the portion within the 

 erect tube is pale straw colour. The dorsal vessel is distinctly seen beneath the skin, and the 

 intestine also, which makes a twist at every segment. They are common in the mud of the Thames. 

 This little Worm is gregarious, and when seen in clear water their movements, each half out 

 of its tube, are interesting. They withdraw into their tubes on alarm, and do not come out again 

 for some time. It is the tail end that projects and not the head. One of these red Worms lives in 

 wet gravel, or sand, or brackish water ;| and a very filiform species, which has a clitellus, lives 

 between tide-marks ;J and another lives as a parasite in the Mussel. 



ORDER POLYCH^ETA. 



These are highly-developed Marine Worms, and they have parapodia, or feet, on their sides, 



furnished with numerous bristles, as their name implies. They have also tentacles, cirri, and 



branchiae. The young are not born like the parent, and undergo a metamorphosis. The sexes are 



usually separate. The Polychseta are divided into two sub-orders : firstly, those which possess 



* Tulifex rivulorum. f Tubifcx Uneata. i Clitcttio arcnarius. 



