102 ANATOMY OF THE ANOPLA. 



fusiform outline, having a dilated middle and two tapering ends. There are also a few small 

 granules and granular cells. The muscular wall and other parts of this chamber agree so closely 

 both structurally and functionally, with the same parts in the Enopla, that it is unnecessary to 

 describe further than refer to the aspect of the parts in the living animal (Plate XIX, fig. 1, o) ; 

 and to the various transverse sections, in which the wall of the chamber is lettered o, and the 

 cavity ao. Sometimes near its diminished posterior end the latter shows a series of monilifora 

 spaces, from internal bridles, and often does not quite reach the tip of the tail. 



In Carinella annulata the proboscidian sheath is not continued to the posterior end of the 

 worm, and it is an interesting fact that this absence coincides, as in the next group, with greatly 

 enlarged lateral vessels. 



The chamber is divided throughout its entire length in Cephalothrios by transverse bands of 

 contractile tissue, so that during the motions of the worm the anterior region is occasionally 

 thrown into many moniliform spaces. These contractile septa (though imperfect in the middle), 

 doubtless prove of much service during rupture, an occurrence so liable in this slender 

 animal. Moreover, the wall of the chamber is thin, and the circular muscular fibres of the body 

 not much developed ; hence the advantages afforded by these safeguards against the inconvenient 

 distension of the chamber during the motions of the worm. The transparent liquid in the cavity 

 contains flask-shaped bodies and minute clear corpuscles. 



Professor Keferstein seems to have had no definite idea of this chamber as a cavity with 

 special muscular walls, but speaks of the peculiar discs as floating in the body-cavity (Leibeshohle) 

 — an error of some importance. In his two transverse sections of Cerehratulus marginatum he 

 appears to have confounded the wall of the tunnel with that of the proboscis. He is thus less 

 correct than several of his predecessors, who noticed the sheath of the proboscis and its 

 contents. 



5. The Proboscis. 



The proboscis in the Lineidce (Plate XIX, fig. 1, a) commences in the form of a somewhat 

 slender tube just in front of the commissures, gradually enlarges, continues for a considerable distance 

 of nearly equal calibre, and then, diminishing, terminates posteriorly in a long muscular ribbon ty, 

 sometimes bifid), which, curving forward in the ordinary state of the parts, becomes attached to 

 the wall of the proboscidian tunnel. Its cavity passes in front into the canal of the snout, and 

 posteriorly terminates in a cul-de-sac at the commencement of the muscular ribbon. It differs 

 from the organ of the Enopla in certain respects, such as the absence of stylets, its more 

 slender proportions, and the shape of the glandular papillae on its internal surface. Experience, 

 indeed, generally enables the observer to distinguish by external characters the proboscis of the 

 Anopla from that of the Enopla in spirit-preparations— by the abrupt diminution of the calibre at 

 the posterior portion in the latter, caused by the presence of the stylet-region and globular 

 reservoir ; but where the organ is incomplete, a transverse section at once puts the question beyond 

 doubt. There are, also, in the proboscis of the Zineidce three longitudinal lines, the first of which 

 corresponds to the intersection of the fibres at one pole, and the other two occur at the ends of 

 the separate segment, hereafter to be described. In the living animal the organ is proportionally 

 longer than in the Enopla, and when rejected is thrown into numerous screw-like coils. 



