as such as far back as the thirtieth bristle-bundle. Moreover, a thick glandular coat
invests the body laterally, enveloping the tori and the setigerous processes in each
segment. In large examples the anterior scutes are rugose transversely, and cut into
various folds in each segment. In Thelepus cincinnatus, Fabr., between the setigerous
process and the hooks from the fourth to the seventh segment a papilla occurs at the
dorsal end of the hook-row, the first being smaller than the rest. These are not readily
seen in the British form, in which the glandular cushions running outward from the
ventral scutes anteriorly are much more prominent. In several from Balta (50 fathoms),
however, these small papillse were present.
In many the posterior region is absent, and it is evident that the fragility of this
part is great, for reproduced tails are common. In a specimen about If inches in
length the regenerated tail (Plate CXX, fig. 1) had a regular series of rounded papillae
externally and a smaller series internally, the anus being in the centre. Slight grooves
pass forward for a short distance from the intervals between the papillse.
The body is of a reddish orange or pale orange inclining to yellow with the tints
deeper anteriorly, and dorsally either pale or dark toward the posterior end. • The
ventral “ scutes ” are white. Most of the specimens from Lochmaddy are without dots;
indeed, only a single example showed a series of reddish-brown specks scattered over
the dorsum, none occurring on the under surface. The first segments are paler than
the succeeding—both dorsally and ventrally, and slightly striated longitudinally. The
tentacles are pale rose; the branchiae pale yellowish.
The cceloniic fluid is abundant in this species.
The intestinal tract consists of a muscular oesophagus with strong circular and
longitudinal non-striated fibres, followed by the more flexible portion with a yellow
glandular coat, then the gizzardj and finally comes the „wrinkled intestine with its
“ chlorogogenous ” sheath. The oesophagus is generally empty; the flaccid region
behind, when the animal has recently fed, has usually three or four large swellings so
as to be moniliform. The contents of these are muddy sand containing organic particles
such as diatoms. In one example the last swelling was partly bounded by the anterior
part of the gizzard, which, however, throughout the rest of its extent was of the normal
size. Dr. Williams states of this “ gizzard-like part” : “ It is generally found on
examination to be devoid of contents; the alimentary substance does not stop or lodge
in it.” In this case the gizzard contained a small quantity of the same muddy sand as
the tract.in front. In the normal condition it is unlikely that over-distension of the
main part of the gizzard ensues, since its function is probably to triturate the muddy
sand and render the organic particles available for absorption, and such would also be
facilitated by the limited quantity in it.
jSegmental Organs.—These are characterised by their greater length than those of
La/nice conchilega, and in the normal condition lie flatly along the ventral wall with
the free ends directed backward. They contain cellulo-granular structures and oil-
globules, and often assume a peculiar moniliform aspect in spirit. In some rounded
bodies like cells occur in masses.
The feet are represented by setigerous processes and tori uncinigeri. The first
setigerous process arises dorso-laterally below the second series of branchias, and the
others follow in succession at the posterior part of each segment. The glandular
investment of the region passes above it, and forms a finished edge dorsally. The
succeeding processes gradually incline to the lateral region, and, posteriorly, to the
ventro-lateral region. The bristles form a vertical fan in each process, narrow at the
base and spreading out distally. Moreover, they are arranged in two alternating series,
a longer and a shorter, the tips of the latter only projecting beyond the surface. They
are shorter than those of Lanice conchilega and less slender, and the wings are more
distinct. Each bristle has a pale base, gently dilates into the widest part of the shaft,
then forms a nearly cylindrical and slightly narrower region to the wings, after which
it tapers to a slender, curved tip. The wings are narrow, both anteriorly and posteriorly
—-the latter having shorter bristles. As G-rube and Marenzeller point out, the bristles
do not, as Malmgren observes, go to the posterior end, a considerable number of the
terminal segments being devoid of them. Thus in an example from Balta about forty
of the posterior segments had no bristles. As the tufts of bristles decrease, the
uncinigerous processes'become more distinct. In imperfectly preserved specimens the
cuticle falls off and the bristles cling to it by their tips, probably from the enlargement
caused by the wings, but the edges of the wings may also be concerned.
The branchiae form two tufts of simple filaments arising from a transverse ridge
on each side on the second and third segments, the anterior ridge being the longer,
passing also further down the side (ventrally), and with more numerous filaments,
which are often prettily waved in a spiral manner when the animal is at rest. They
are of a pale, straw or deep orange colour with a red streak in the centre from the
blood-vessel, which is most distinct immediately after a contractile wave of the body
drives the fluid forward. As they arise from two segments they can scarcely be called
“ one pair ” as in the * Catalogue of Worms5 in the British Museum. In a young
example, half an inch in length, these organs formed two distinct groups on each side,
the first containing two or three filaments of different lengths, the posterior only one.
They are enveloped in a transparent structureless cuticle, and the hypoderm has finer
cells and granules than the tentacles. Longitudinal and circular muscular fibres are
also present. The branchiae seem to vary in the genus, and some of the largest examples
of T. cincinnatus from the Arctic Seas have short, thick filaments. As regards origin
and structure, the British form corresponds generally with the northern type just
mentioned.
The bristle-tufts range from thirty to forty-one, and in transverse section
the bristles are somewhat ovate, sometimes approaching a short or blunt ellipse. The
anterior bristles have smooth straight shafts with curved, winged tips which taper to
a fine point (Plate CXXVI, fig. 6). The wings are of moderate width and disappear
before reaching the tip. The winged tips of the shorter series alone project beyond
the setigerous process, and they have a more or less alternate arrangement with the
longer series.
The posterior bristles are much reduced in size and the greater part of the shaft
is deeply imbedded in the tissues, the translucent free portion having the shaft somewhat
dilated at the commencement of the wings, which are rudimentary, and almost reach
the surface of the setigerous process. In the most posterior forms the slender shaft