78 W. C. M'INTOSH ON VALENCINIA ARMAND1. 



of the worm. The greatly developed layer of circular muscular fibres must exercise a 

 special influence on this region of the alimentary canal, probably as an oesophageal con- 

 strictor. The arrangement is one common in the Carinellidse. 



The proboscidian sheath (a o) commences, as usual, at the incurvation in front of the 

 ganglia, and, as formerly described, becomes more or less atrophied behind the mouth, 

 while the great inner circular layer developed from its outer fibres acts as the chief 

 constrictor for this chamber as well as the alimentary canal. At first (figs. 3 & 4, a o) it 

 clearly possesses two muscular layers, an external circular and internal longitudinal ; but 

 after the change behind the mouth is completely established, all that can be noticed 

 inferiorly is a circular band in the tissue of the upper layer of the digestive chamber. A 

 reversion to the primary condition ensues on the diminution of the inner circular 

 muscular layer, the proboscidian sheath striking off from the latter and the alimentary 

 wall as a special tube, which is continued to the posterior end of the worm, where, 

 however, it forms an extremely small chamber (fig. 8, ao). In Carinella annulata it is 

 not continued to the posterior region of the body, and, as formerly observed, absence 

 or diminution of the proboscidian chamber (*. e. the cavity within the sheath) in the 

 Lineidse and Carinellidse is accompanied by greatly enlarged lateral vessels. 



The proboscis (figs. 4 & 7, A) agrees with that of the Carinellidee ; but its very minute 

 size prevented an accurate discrimination of the external region into two layers. It had 

 the aspect of an elastic coat with external circular fibres. A reexamination of more 

 favourable examples of the proboscides of the Carinellidse has enabled me to correct an 

 error into which I fell on a former occasion, in stating that the external coat consisted 

 of elastic, and the next of circular muscular fibres. The latter are external, and the 

 structureless elastic internal. The next layer in Valencinia Armandi consists of a 

 powerful longitudinal muscular coat ; then comes a considerable circular muscular layer, 

 upon which the glandular Lining of the organ rests. The glandular papillae, as usual 5 

 contain many rod-like bodies. The proboscis terminates posteriorly in a ribbon of lon- 

 gitudinal fibres. 



Digestive System.— The mouth (in transverse section, fig. 3, to) forms a small lon- 

 gitudinal slit a little behind the ganglia, and is much less prominent than in V. linei- 

 formis, as well as more anterior in position. It leads into the glandular oesophageal 

 region, which soon becomes clasped by the powerful internal circular muscular layer 

 formerly alluded to (figs. 5 & Q,j). The walls of this region are thinner, but of firmer 

 consistence than the succeeding portion, which commences near the termination of the 

 special circular muscular layer. In transverse section (fig. 7, f) the densest masses of 

 the refracting (fatty ?) granules, which form the chief portion of the wall, lie on each side 

 above the nerve-trunks, while a layer beneath the proboscidian sheath joins them supe- 

 riorly, and a V-shaped bend ventrally completes the circuit. Towards the posterior end 

 of the body (fig. 8, /) the canal assumes the form of an ellipse in transverse section, the 

 • walls are lax, translucent, and more finely granular, and the cilia appear to be longer. 

 It is held in position in this region by circular fibres and vertical bands. 



Nervous System. — There is nothing special in the structure of the ganglia, which, near 

 their commissures, are seen in fig. 3, h ; but the presence of a special longitudinal series 



