Mr. J. L. Clarke on Lumbricus terrestris. 251 



Before treating of the nervous system it was necessary — in order to 

 show the proper functions of many of its parts — to give some account 

 of tlie organs of prehension, deglutition and digestion ; and as these 

 are insufficiently explained elsewhere, the author has described them 

 entirely from his own dissections and observation. 



The first anterior segment is a conical or nipple-shaped projection in- 

 serted behind into the upper fifth of the second segment, or first ring. 

 Its dorsal surface is covered, except in the centre, by concentric laminae 

 and irregular masses of pigment-granules, which are interspersed 

 with large, peculiar and nearly pellucid cells. Its under part forms 

 a soft and delicate pad, or upper lip, and is continuous at the sides 

 with the inferior half of the second segment, or under lip, to complete 

 the oral orifice from which the mucous membrane of the mouth is 

 reflected inwards. The mouth is a wide tube surroiuided by a deli- 

 cate muscular coat, and attached to the outer tube, or rings, by fine 

 muscular bands. Behind, it dilates into a capacious heart-shaped 

 sac, of which the roof or upper wall is covered by a thick oval mus- 

 cular mass. The outer portion of this mass is divided into distinct, 

 radiating, digital muscles which connect it on all sides and are con- 

 tinuous with the longitudinal muscles of the rings. Its inner surface 

 projects anteriorly into the cavity of the pharynx, in the form of a 

 thick circular disc or sucker, surrounded by loose folds of mucous 

 membrane. Opening into the sides of the mouth and pharynx are 

 two or three sets of salivary glands, which consist of convoluted 

 tubules, resembling those of Lepidopterous insects : these glands have 

 not been hitherto detected in Lumbricus terrestris. The pharynx 

 contracts into a comparatively narrow oesophagus, which in its turn 

 dilates into a capacious crop ; and this immediately opens into a 

 cylindrical gizzard composed of a ring of cartilage, with an external 

 muscular coat, and a lining of mucous membrane. A long straight 

 and narrow intestine extends through the rest of the body, and is 

 covered throughout with yellow, follicular, hepatic glands in circles 

 corresponding to the segments. 



Nervous System. — The central organs of the nervous system con- 

 sist chiefly of a bilobed cephalic ganglion, and a double chain of sub- 

 ventral ganglia extending through the whole length of the body. 

 The lateral lobes of the cephalic ganglion are pyriform, and united 

 . by their broader ends in the mesial line. The small end of each 

 divides into two nerve-trunks, of which one forms the root of its 

 cephalic nerves, and the other, the pharyngeal cms, which curves 

 round the side of the pharynx to join the first subventral ganglion. 

 Each cms gives off eight or nine branches. The first four or five arise 

 from the under part of its anterior half, and immediately enter the 

 upper surface of a minute and delicate cord-like chain of ganglia, the 

 enlargements of which correspond to them in number and size. This 

 highly interesting structure lies on the side of the pharynx, con- 

 cealed beneath the cms. The breadth of its first ganglionic enlarge- 

 ment in a good-sized worm, was the 2~^oth of an inch ; that of the 

 last the lio^h ; the pharyngeal cms, where their roots come off, was 

 •j-^th of an inch in diameter. Each border of the chain gives oflf 



