PROBOSCIS. 69 



inner surface thrown into very prominent rugae, which sometimes appear like large papillae 

 covered with the characteristic glands of the cavity. These plaits are not mere wrinkles and 

 folds caused by the contraction of the organ, but are present under great pressure (Plate XII, 

 fig. 13). The granules of the peculiar fluid therein are also conspicuous. It may here be men- 

 tioned that after prolonged confinement the integrity of the proboscis in this and other species is 

 affected, the stylets degenerating, and even disappearing altogether, both from the central and 

 marginal structures. Not only is this the case in the adults themselves, but under the same cir- 

 cumstances the more advanced young in the interior of ProsorJiochmus Claparedii undergo a 

 like degeneration. In a specimen of N. Neesii where this had occurred, the wave of the 

 molecular fluid driven forward by the contraction of the reservoir distended the muscular 

 cavity (e) at the front of the granular basal apparatus (which in this instance was devoid of a 

 stylet) ; and as the aperture into the anterior chamber permitted only a limited discharge at a 

 time, the fluid rushed into the centre of the granular structure, and distended it and its wedge- 

 shaped setting with every impulse. The absence of proper nutriment and free aeration, for the 

 salt water was but rarely changed during the year, are sufficient causes for the above-mentioned 

 degeneration. 



In Nemertes carcinopMla the proboscis and its apparatus are reduced to a minimum. The 

 anterior region (Plate XII, fig. 14, a) is very short, and has an almost conical outline, the base of 

 the cone being formed by the floor of the chamber. Its wall is proportionally thick and muscular, 

 and the tube has a granular aspect internally, a condition probably due to indications of papillae. 

 Posteriorly it terminates in the usual floor, into which, however, only one aperture leads, viz., that 

 of the central stylet. The stylet-region, while still retaining the type of the Enopla, differs much 

 from that of any other British species. Instead of the ordinary well-defined arrangement of longi- 

 tudinal and radiating fibres, the entire muscular structure is obscured by numerous granular or 

 cellulo-granular bodies (y). There is no trace of marginal stylet-sacs. The central stylet is 

 minute, and furnished with an elongated and faintly granular basal apparatus, which is fixed in the 

 usual transparent muscular investment. The mobile chamber ( £ ), into which the ejaculatory duct 

 opens, is in the ordinary position. Though the whole apparatus is very minute, the stylet has been 

 observed to be thrust forward by the contraction of the fibres of its basal investment, so that its 

 point projected into the anterior chamber of the proboscis. The ejaculatory duct is large, and, 

 from its central position in ordinary examinations, causes the stylet-region proper to appear 

 bifid posteriorly ; but this is due only to the greater translucency of the duct, which, for the time, 

 makes a separation between the dense granular masses at the sides. The region of the reservoir 

 is fairly developed, the wall being formed chiefly of muscular fibres having the usual spiral 

 arrangement, and the inner surface covered with granular glands. Occasionally the reservoir 

 contracts with force, and drives the contents forward into the ejaculatory duct and muscular 

 space behind the floor of the first region. The channel of the reservoir leads into a posterior 

 chamber of comparatively small dimensions, but having rather thick walls, and terminating 

 in a cul-de-sac and bulbous end a short distance behind the oesophageal apparatus of the 

 animal. The cavity has a cellulo-granular lining internally, and in some specimens 

 the terminal portion is distended by a transparent fluid containing a few compound cells 

 of similar aspect to those found in other species. It is kept in position by fibres from the 

 strong bands at the posterior part of the oesophageal region of the digestive chamber. All 

 M. van Beneden states with regard to the structure of this organ is that it is very short, and 



