EEPORT ON THE ANNELIDA. 
377 
otherwise than in fragments, and these often quite pulpy. The spirit does not seem to 
gain access to the middle and posterior jDarts of the tube, so as to counteract the 
softening of the animal in its own fluids or sea- water. Not more than a single 
PhyllochcBtopterus existed in any tube, but occasionally two examples of the Polynoe 
were found, either together, or one in front and another behind. In the latter case, 
however, no diaphragm was present, so that the second specimen may have entered 
accidentally. The Polynoe keeps the entrance to the tube, just in front of the tentacles, 
its own palpi often projecting from the aperture. In order to thrust out its tentacles 
the PhyllochcBtopterus must therefore glide past the Polynoe, the narrow, flattened 
body of which is specially adapted for its peculiar habitat. The Polynoidse are 
remarkable for the frequency with which they haunt the tubes of Annelids as w^ell 
as other organisms. 
The intestinal pellets consist of a fine greyish mud rich in Diatoms, sponge-spicules, 
fragments of Radiolarians, and many other minute structures. 
The cuticle in transverse section of the anterior third (PI. XXXVIa. fig. 3) is only 
seen here and there as a firm clear margin to the hypoderm. Its development, there- 
fore, is slight, and, indeed, it is doubtful whether it could be removed as a separate layer. 
The condition of the preparations (to which the spirit had gained a too tardy access 
in the tubes), however, is unfavourable for decision in this respect. No feature, on 
the other hand, is more pronounced than the great prominence of the hypoderm, 
which forms a dense layer, almost a third of the whole thickness of the body, on the 
ventral surface. The long cells are arranged in parallel rows, and the coat thus readily 
splits in that direction. It is coloured pure white. The hypoderm, while much 
thinner than on the former region, forms a considerable layer laterally and again on 
the dorsum, where a thickened ridge occurs on each side of the median line. The 
ovoid nerve-cords are widely separated, but they are of large size. They occupy a 
hollow below and internal to the homologues of the longitudinal ventral muscles, and 
have ventrally the dense layer of white hypoderm, while externally and superiorly is the 
pale lateral hypoderm, also of considerable depth. A thin but continuous circular muscular 
layer lies beneath the latter coat. The longitudinal dorsal muscles form a triangular 
area on each side of the upper part of the alimentary region, the superior fibres 
forming an arch over it and closely approaching each other in the middle line, while 
the inferior apparently become continuous with the longitudinal muscular coat of the 
alimentary sheath. As in the common Chcetopterus of Britain, many vertical muscular 
bands pass through the chief mass of the longitudinal dorsal, and in the preparations 
these bound numerous spaces, which, however, may partly be due to rupture after 
immersion in spirit. The condition is diagnostic when compared with the common form 
just mentioned. The vertical fibres pass at intervals to join the circular coat ventrally 
at a point internal to the nerve-trunk. The comparatively small longitudinal 
(ZOOL. CHALL. EXP. — PART XXXIV. — 1885.) LI 48 
