middle of the bristled region the longer pale golden bristles have stout striated shafts
(Plate CXXVa, fig. 8) of nearly equal diameter, and tapering tips with wings. Many
of these seem to have been broken in life, and show modified tips. The striaa at the
commencement of the wings are oblique. The shorter bristles are more translucent and
have either no wings on the free portion or very narrow ones.
The hooks commence on the segment behind that described as having the
triangular fold in a line with the last branchia—that is they occur in the segment
behind the hranchige. At first they are in a single row, but by-and-by they form an
alternate double row along the centre of the ridges which pass in front from the .bases
of the setigerous papillge to the edge of the ventral scutes, and behind these almost
to the mid-ventral line. With the cessation of the bristles a change ensues, for the
hooks are now borne on a prominent lamella—slightly crescentic or scoop-shaped, and
placed laterally at the posterior edge of each segment—which still consists of two rings.
These lamellas diminish in size posteriorly, becoming minute towards the tip of the
tail. On these lamelliu the hooks form a close series in a single row. The hooks
(Plate CXXVa, fig. 8 a) are distinguished by their elongated basal region, which has
a median convexity, then curves upward at the anterior edge, which has a small
process for the ligament. A process also occurs on the anterior margin about its middle,
a double curve meeting at this point. The large fang is well developed and has only a
single tooth above it in lateral view. The posterior margin has a deep incurvation.
The hooks vary chiefly in the shape of the basal region.
The alimentary canal consists of mouth, muscular gullet, which is firm, narrow and
dull greyish in colour, with many blood-vessels on its walls. It joins the dilated orange
region, with its highly rugose glandular walls and the longitudinal bands of muscles.
This terminates in the pale and wide gut which leads to the vent.
Food.—The muddy sand in the gut was loaded with sponge-spicules, diatoms,
Foraminifera and organic particles of various kinds.
Reproduction.—In June amongst the perivisceral corpuscles were numerous ova
which were much larger than the former by one to three diameters, and which varied
considerably in size. Each had a zona, granular contents, a clear nucleus, and one or
more nucleoli. The ova are developed in the paired, long strap or tongue-shaped ovaries,
which arise ventral of the bristle-bundles in the anterior region. They are longest in
front, and extend as far forward as the branchiae. The long anterior organs appeared to
be empty, only the cilia occurring internally. They soon, however, had ova in their
interior and many of the posterior were laden with them. These posterior processes
were shorter, broader, and more plume-like. They are attached to the body-wall inside
but close to the bristle-bundle, and probably represent those nephridia which transmit
the reproductive elements.
Penvisceral fluid.—This is coloured of a reddish hue and consists of a vast series of
ovoid corpuscles filled with yellowish granules, and may possess in addition one or more
larger clear circular vesicles, which, however, may be connected with katabolic changes.
The corpuscles altered their outline by pressure against each other, and broke up into
smaller cells with protoplasmic processes projecting from their surfaces.
The muscular fibres of the body-wall form a series of strands, both longitudinal and
circular, anteriorly over the swollen thoracic region. Two circular bands occur in each
segment, whilst the longitudinal are in numerous separate strands, which give the dorsum
a corded appearance.
Two varieties occur, viz., the large littoral form from Lochmaddy, and those from
deep water, which are smaller.
Commensals.—In North Uist, as at Lochmaddy, Polyno'e scolopendrina of large size
is frequently met with in the tubes of this Terebellid.' It is hard to conjecture how the
soft—almost semi-gelatinous—annelid tolerates the stiff, hard-spined Polyno'e, but it
shows no signs of uneasiness or injury, and the Polyno'e must supply itself with food either
independently or from the catering of the Terebella. Very rarely was this commensal
found in the numerous examples procured from the Channel Islands (Guernsey and Herm),
and thus they were in contrast with those from Lochmaddy. Nor was a Polyno'e found in
those from Scalloway.
The tube of this form is composed of small stones, fragments of shells, or in certain
cases, as in Ireland, fragments of slate with secretion, and it is loosely bound together,
the cement readily giving way on attempting to remove it from its site. Some of the
tubes are three-quarters of an inch in diameter, and they may be in the form of a long
arch on a stone or rock; the annelid, taking advantage of the surface of the stone, thus
saves both labour and materials. The tubes occur in some cases in groups or small
colonies on congenial sites. The tube of one from Valentia Harbour is composed of
fragments of leaves and other vegetable structures and fibres, the whole forming a
soft tube.
An excellent account of the formation of the tube in confinement is given by De St.
Joseph (1894). This author also states that in dredged examples the general colour is
cinnamon with numerous white points, and thus corresponds with the so-called Terebella
Meckelii. He mentions the occurrence of a papilla under the second pair of branchiae, and
the same on the five succeeding segments between the setigerous process and the torus.
. Habits.—When seized in its tube it often breaks itself behind the bristled region, the
“ suicidal mark” of the Terebellids. Few species, indeed, are more irritable, for when
touched it breaks off the posterior region, and almost always does so, even when cautiously
lifted. Yet it swims actively when placed in water. It is not luminous.
Reproduction.—Ray Lankester1 (1873) during the winter at Naples found the
eggs in abundance, and observes that “ a delicate chorion forms round the egg after
segmentation, on the surface of the cleavage-cells, which are densely ciliated,” and that
“ the cilia were really processes of the protoplasm of the cells ” and could be drawn
through the chorion, which they perforated.
Lo Bianco (1909) found that the period of reproduction at Naples, where the species
is termed “ Terebelle,” was between August and May, most, however, occurring between
January and April. The yellowish-orange ova are enveloped in a gelatinous matrix
2—4 cm. in diameter (fissato sull* orlo del tubo).
A careful account of the development of this species was given by Milne Edwards
in 1844.®
1 Vide p. 100.
2 Vide p. 96.