ANNULOSA: ANNELIDA. 263 



bristles attached in rows to the sides and ventral surface of the 

 body. No branchice are present. They are all hermaphrodite ; 

 and the young pass through no metamorphosis. The Oligochceta 

 are divided into the two groups of the Terricolcz or Earth-worms, 

 and the Limicola or Mud-worms and Water-worms (Scenuridce 

 and Naididce). 



In the common Earth-worm (Lumbricus) the body is" cylin- 

 drical, attenuated at both extremities, and carrying in the adult 

 a thickened zone, which occupies from six to nine rings in 

 the anterior part of the body, is connected with reproduc- 

 tion, and is termed the " clitellum," or " saddle." Locomo- 

 tion is effected by eight rows of short bristles or setae, four of 

 which are placed laterally and four on the ventral surface of 

 the body ; these representing the foot-tubercles of the higher 

 Annelides. The mouth is edentulous, and opens by a muscu- 

 lar pharynx into a short oesophagus, which leads to a muscular 

 crop, or " pro-ventriculus," succeeded by a second muscular 

 dilatation, or gizzard. Salivary glands open into the pharynx, 

 and other glands, probably digestive, open into the gullet. 

 The intestine is continued straight to the anus, and is con- 

 stricted in its course by numerous transverse septa, springing 

 from the walls of the perivisceral cavity. The perivisceral 

 cavity (as in all the Oligochata) is lined by a cellular mem- 

 brane, which is continuous with a yellow cellular layer cover- 

 ing the intestine and large vessels, and which casts off its cells 

 into the perivisceral fluid. The pseudohaemal system consists 

 of three principal longitudinal trunks and their branches, filled 

 with a red non-corpusculated fluid ; and there exists, in even 

 greater numbers, the same series of lateral sacculi or " segmen- 

 tal organs " which we have seen in the Leeches, and which 

 have either a respiratory or a renal function. In all the 

 Oligochata the segmental organs communicate internally with 

 the perivisceral cavity as well as externally with the outer 

 medium. A portion of the segmental organs is ciliated, and 

 in all cases the segmental organs of certain of the segments 

 have the special function of acting as efferent ducts for the 

 generative organs. The body-cavity is filled with a colourless 

 corpusculated "blood." The reproductive organs consist of 

 two pairs of testes, opening on the fifteenth segment, and one 

 pair of ovaries, of which the oviducts open on the fourteenth 

 segment. In addition, the animal also possesses a pair of 

 seminal reservoirs in the tenth and eleventh rings, and five 

 pairs of glands for secreting the capsules of the eggs. The 

 ova are deposited in chitinous capsules, and the young pass 

 through no metamorphosis. 



