bristle-tuft and a small subulate cirrus external to or behind it. The first has the
longest and largest cirrus, and it is situated to the exterior of the bristle-tuft, and the
next five' or six, though less, are easily seen to the exterior of the bristles. By-and-by,
in their progress backward, they diminish and fall to the rear of the bristle-tuft, and in
the caudal region they form only flattened eminences behind the tufts. The first torus
for the hooks of great length, and so with the second, but the others gradually
diminish, the last eight or nine being cirriform. The hooks (Plate CXXIII, fig. 3 e) are
similar to those of 8. spinulosa, presenting six teeth in lateral view; the basal end, however,
is somewhat more truncate distally. Front views show at least a double series of teeth
along the edge. Each has its distal and two proximal tendons, and the numbers are
great, the tendons forming an asbestos-like mass of fibres in each case. The posterior
hooks are smaller, but do not differ materially in outline.
The first bristle-tuft of the region is directed horizontally inward, and in structure
it possesses intermediate characters, having about six or aeven strong golden bristles
with long flattened oar-shaped tips and elongated points, the surface of the tip being
minutely spinous. There are, besides, about the same number of forms with more
slender shafts and finely tapered tips, densely covered with minute whorls of
spikes.
The second ventral tuft of pale golden bristles is directed inward and slightly
forward, but it conforms to the ventral type of structure, some of the bristles having
stouter longitudinally striated shafts, others more slender, but all having slender tapering
tips clothed with whorls of spikes directed distally. The rest of the bristles of the
region have their tips directed forward and inward, those in the caudal region being even
more conspicuous than those in front, and they-have proportionally shorter tips and
longer shafts, the imbricated spikes forming a scale-like arrangement on the front of the
bristle, whilst the back is smooth. A more or less alternating series of stronger and
more slender bristles occurs in each tuft, which is antero-posteriorly spread, like a fan
over the soft caudal tube in its ventral groove. Arnold Watson is of opinion that the
function of the ventral bristles is largely connected with the passage of the waste matter
for ward, and they keep the caudal appendage in a central position. He met with an
abnormality at the eighteenth abdominal foot which had an extra fascicle of bristles
about half the size of the ordinary one and situated internally.
The caudal tube bends smoothly to the ventral groove, and extends more than halfway
forward on “the ventral surface, diminishing a little as it proceeds. A purplish-
brown pigment patch marks, its commencement. Two ridges (probably muscular) occur
on the ventral surface, with a median groove between them and a lateral furrow at each
side. The anal aperture at the tip is usually ovoid in the preparations, with the long
diameter transverse.
Arnold Watson has found the intestine infested with Selenidium even in young
worms only 2 mm. long. In another sickly young specimen a group of parasitic
Nematodes (?) were waving out of the anus.
In a very young example with two eye-specks, Arnold Watson observed two light
brown bodies at the junction of the caudal process with the trunk, and noticed that the
peristaltic action of the gut was from behind forward. He also observed glandular pores
round the margin of the lower lip. The mucous ribs or folds sloped obliquely from the
median ventral ridge and met at an angle in the mid-dorsal line. He evaginated the
caudal tube, which showed a spiral or oblique arrangement of ribs internally with a
ventral ridge apparently in connection with the expulsion of the excreta. The inner
lining was infested by parasitic worms (Nematodes ?)
Eye-spots occur in young forms (Fig. 140), after the disappearance of the central
cirrus, at the V_shaped origin of the ridge anteriorly. The cirri at each side of
the building organ appear to be proportionally larger in the very young forms
(Arnold Watson).
Arnold Watson observes “ that the position of the nephridiopores for the emission of
ova is on the posterior face of the uncinigerous lobes, whilst the pores for 1he emission
of sperms are on the dorsum just behind the base of the branchial processes.” “ The
pores of the head-kidney are in the angle formed by the first pair of branchim with
the body.”
jReproduction.—Specimens from Naples (probably procured in summer) had ova of
Fig. 140.—Sketch of the folds and eye-spots of a young example of r., ridge; op.l., opercular lobes. After an outline bSya hAerlnlaorlida Walvaetosolant.a. oc., eye-spots;
considerable size in the coelomic space. Lo Bianco (1893 and 1909) states that artificial
fecundation was carried out at Naples between September and June. Arnold Watson
mentions that the ova are cream-coloured, or, at any rate, much less tinged with pink,
and smaller than those of S. spinulosa.
Tubes.—Considerable masses of the tubes (Plate CXVIII, fig. 2) are found in the
estuaries of many English rivers, composed either of fine or coarse sand-particles sometimes
dotted over with pure white Foraminifera, as if sparsely studded with pearls.
The coarse tube figured by Chenu (1843-53) might pass for that of Tetreres murata,
Allen, if indeed it is not that form.
An interesting variation in thé form of the tube was procured by Arnold Watson at
St. Mawes, in which the aperture of each tube had a broad flat projection like a shield over
it, and composed of the. same coarse grains of sand as the rest of the structure. He
considers that this addition may have some relation to the intensity of the light in the
situation chosen by the annelid, though it is possible that protection from certain enemies
may also be a reason. In watching the building operations of a young example, Mr.
Watson observed the grains of sand rotated and held in place by the “ palps,” the lips by
their sucker-action meantime covering them with cement. After a number of grains had