Body somewhat, elongated, narrowed posteriorly, from ^ to § inch in length, though
sometimes longer. Segments from twenty-two to forty-two. Colour pale yellowish
throughout, in some faintly marked with brown towards the posterior end, especially
between the feet. In others the dorsum is speckled with brownish spots, arranged transversely,
and numerous yellowish specks. The naked portion behind the scales (including
the bases of the feet) is speckled with yellowish and whitish. In some Scotch examples the
dorsum is of a blackish hue, interrupted by numerous fine transverse lines, most marked
at the segment-junctions. In others a distinct band of dark pigment, interrupted by
numerous pale strige, most marked at the segment-junctions, passes along the dorsum.
The ventral surface is pale. The segmental eminence is prominent, but the papilla is
very small. Posteriorly the body terminates in two caudal styles.
Proboscis.—In extension this organ, in the preparation shows apparently thinner
walls than in the ordinary forms. A wide canal thus exists in the centre, and the teeth
of the dorsal and ventral arches are widely separated. The usual nine papillaa occur on
each arch. The teeth are pale brown (amber-coloured).
Scales (Plate XXXIII, fig. 7) cover the dorsum in front* but leave the centre bare
posteriorly. The normal number seems to be eighteen pairs, but few examples are
complete in this respect. They are more or less rounded or ovate translucent organs,
so that their minute structure is readily shown. The entire scale is minutely dotted, and
its areolae so arranged that the whole has the aspect of a transparent plate. The dots,
as Ehlers stated, appear to be in the cuticular layer of the under surface of the scale.
The outer and posterior portions of the scale, moreover, are -studded dorsally with a
series of small papillge (modifications of cilia) of a cylindrical or clavate outline, many of
which run in the lines of the finely branched nerves. In life these structures have
minute papillaa or palpocils at the top, so that they probably perform the function of
special tactile organs, as indeed the able description of Ehlers would lead us to expect.
Only a small portion at the anterior and inner area of the scale is devoid of them, and
the nerves seem to terminate there in special end-organs. In addition, a series of much
larger clavate processes occurs thinly scattered- over the same region (outer and
posterior), the largest sometimes projecting at the posterior border. They are readily
seen under a lens, standing out like minute pillars from the surface of the scale. These
receive nerve-twigs from the main branches, as shown by De St.-Joseph. The outer
and posterior borders, further, are beset with a closely arranged series of short globular
cilia, which also occur on the surface adjoining the edge. Many of these have microscopic
papillae (modifications of palpocils) at the tip, and all show a minutely granular
central area—connected by the pedicle with the central connective tissue.
The nerve-supply of these organs is clearly outlined, as originally described by
Ehlers, and subsequently by Langerhans. At the posterior border of the scar for the
pedicle an enlargement (ganglionic) occurs, from which a main stem, rapidly breaking
up into branches, proceeds posteriorly, giving off twigs in a somewhat dichotomous
manner to the greater part of the scale, while a considerable branch goes forward, or
obliquely forward and outward, to complete the distribution. The smooth pale area at
the anterior and inner bolder has the smallest branch, probably because its functions
are less prominent. The nerve-twigs terminate in peculiar granular swellings—mentioned
by Ehlers. Every little papilla has its nerve-twig, and the granular enlargements
are connected with the system like fruit on the tips of a much ramified wall-tree.
In life the scales are quite translucent, sometimes presenting towards their anterior
and posterior borders numerous yellow patches at the papillae, or, as in the figure,
simply dotted with white specks. In others they have a faint purplish-brown tinge,1
enlivened by orange and yellowish specks. The brownish tinge in some is towards the
inner border.
This active and irritable annelid frequently throws off its scales, but, as in other
cases, they are readily reproduced, an interesting account of their development having
been given by Ehlers.
De St.-Joseph found a number óf specimens of Pedicellina belgica, van Beneden,
on the under surface of the scales.
Feet^Ê-The first foot has a spine, but no bristles in the available specimens. De
St.-Joseph thinks this is the normal condition, but it is uncertain.
The dorsal division of the foot (Plate XXX, fig. 9) forms a short and broad process
bearing a series of translucent slightly curved bristles (Plate XL, fig. 17), which are not
much tapered distally. The rows of spines (or frills), about eight in number, are wide
apart inferiorly, while the tip of the bristle; is notched as if from a minute claw or
secondary process. So homogeneous are these bristles that the usual longitudinal striae
have disappeared, and they resemble crystalline structures. In the ventral division
the spine forms the apex of a somewhat conical lobe, the upper slope, however, being
the shorter. The bristles (Plate XL, fig. 18) are equally transparent, but are slender
and elongate, the shaft terminating superiorly in a dilatation with a spinous frill, which,
like those of the dorsal, seems to be continuous. From this part the spinous region
passes with a slight bend towards the dorsum, and ends in a well-marked hook with a
small secondary process—apart from its base beneath. The tip is flattened and not
much tapered, while the oblique rows of spines are somewhat adpressed. Little
change takes place in their structure in the posterior feet. The bristles seem to have
few parasites.
Thé dorsal cirri (Plate XL, fig. 19) are comparatively long, with a slightly dilated
portion beneath the long filiform tip. A yellowish .belt, or in some a white ring,
marks the dilated portion. A few minute clavate cilia occur on their surface, and to
these nerve-twigs proceed. The nerve in the centre of the cilium appears to form an
enlargement in the opaque region at the base of the filamentous tip, and then continues
onward to the extremity. The posterior cirri are longer and more slender, and the
dilatation below the filiform tip is distinct.
The ventral cirri are rather long, smooth and tapering, their tips extending beyond
the bases of the bristles.
Reproduction.—Specimens procured in Bressay Sound in July showed ripe eggs,
and they were extruded in masses on rupture, of the body. A male captured off Peel,
in the Irish Sea, bore ripe spermatozoa the same month.
Development.—A young form measuring a little oyer 1 mm. occurred amongst the
1 De St.-Joseph calls it roseate.