eminence probably associated with tube-formation. No eyes are visible in the preparation
behind the cephalic collar.
The body has 120—150 segments, and is characterised by its great proportional
length and slenderness posteriorly, as well as. by its pale cream-colour, here and there
enlivened by the blood-vessels and the brownish-red specks posteriorly. The enlarged
anterior end has, further, a close series of transverse ridges which have a minutely
tessellated appearance from isolated glandular masses arranged transversely. These
glands have, besides the granules, clear refracting cells and globules. The separation
of the longitudinal dorsal muscular fibres in this region also increases its tessellated
aspect. Behind the bristled region the body gradually narrows, and ends in a slender
tail with a terminal anus surrounded by marginal papillae. The dorsal surface is convex,
the ventral flattened anteriorly and grooved posteriorly. The glandular shields or
plates in front are about twelve in number, with a few (three or four) additional
small median processes. Behind the region of the shields is a median groove with a
prominent ridge on each side. At first lateral, these ridges gradually pass to the
mid-ventral line, forming posteriorly a raised belt with a median fissure, then widen
a little toward the tail, where the papillse for the hooks occur in the line of each
moniliform ridge, and gradually diminish as the tip is reached.
Whilst the segments in front have several marrow rings dorsally—giving a finely
ribbed aspect to the surface—the narrow posterior region has only the segment-junction
separating each smooth segment. The Mediterranean forms appear to be similar in
colour to those from the Channel Islands, viz., yellowish-grey.__
Behind the lower lip is apparently a segment with a narrow ventral shield. The
next bears the first, and larger, pair of branchiae, each springing from a short stalk
and rapidly giving off four main divisions, which split up, after a brief course,
into a sub-dichotomously divided tuft with comparatively short terminal branches,
the whole forming a dense arbuscle. The second, and smaller, pair is on the next
segment and has a similar structure. Occasionally a specimen has three' branchiae
on one side and two on the other, the third being a small independent stem behind
the second.
Yentralward of the second branchial stalk is a small conical papilla which represents
the first setigerous process, though it has no bristles. The next setigerous process has a
well-developed tuft of bristles, which are pale, translucent, rather brittle, and in two
groups, the longer forms (Plate CXXVa, fig. 2) have long, straight, deeply inserted
shafts, which are nearly cylindrical to the commencement of the wings from which they
taper to a delicate point. The wings have a characteristic expansion at the base, are
narrow distally, and show no serrations. The shorter bristles (Plate CXXVa, fig. 2 a),
have peculiarly curved, tapering, serrated tips without distinct wings. Whilst the two
setigerous processes behind the branchise remain isolated and simple, the third presents
two processes, viz., the setigerous, and an antero-ventral papilla, and these continue in
the six subsequent feet, the following (from the tenth) setigerous processes, which are
somewhat conical, though antero-posteriorly flattened, remaining simple, and the first
(tenth) of the (posterior) series having a small papilla below it, at the end of the hook-
row. There are twenty pairs of bristle-tufts. The glandular cushions between the
bristle-tufts in front assume the form of papillm. Marenzeller mentions that» the
setigerous processes are crenate at the convex tip, but this was not evident in those
examined.
The first hooks occur opposite the third setigerous process—that is, the second behind
the branchiae—and they occupy the summit of the elevated ridge which extends from the
bristle-tuft downward to the ventral grove, and cover, in short, the external aspect of the
ventral longitudinal muscles. They are in a single row in the first six segments, but
the rest are in a double row, and this continues to the commencement of the last thirty.
After the cessation of the bristles the uncinigerous processes form transverse crescents in
each segment, gradually, however, becoming smaller, until on the slender terminal region
in front of the tail they form a series of papillae, so that the ventral ridge on each side is
moniliform. The first hooks are distinguished (Plate CXXVa, fig. 2 b) by the great size
of the main fang, which has a crown of. small hooks above it, about three being usually
visible in lateral view, and by the comparatively small size and oblique nature of the base,
which has above its dorsal angle an abrupt incurvation, whilst on its anterior edge it has
a sharp point, for the attachment of a tendon, and a gentle incurvation beneath it. The
modified form of these early hooks is indicated by the imperfect condition of those at the
end of the -row. By-and-by they form a double row and assume the typical condition in
which the great fang is proportionally smaller (Plate CXXVa, fig. 2 c), the base less
elongated, its lower edge more convex, and the curve below the point on the anterior
edge less pronounced. About four small hooks are visible above the great fang in
lateral view.
The Amphitrite Tondi of Delle Chiaje1 (1828) is a form having two bran chi as, but the
description is so brief, and the figure so indefinite, that it is uncertain whether it refers to
A. scylla or not.
This species was entered by Be Quatrefages (1865) under two titles,'viz., Savigny’s,
and again as the Physalia gracilis of G-rube.
A form with three branchias, but otherwise closely resembling the above in the
cephalic region, intersetigerous papilke, bristles and hooks, occurs occasionally between
tide-marks in Guernsey and Herm. It would’ appear to bej another instance of the
variability of these organs (branchise) in a common species.
De St. Joseph (1894) describes a single pair of segmental organs in the third
segment, with a ciliated funnel internally, and a reddish-brown outer region which opens
between the setigerous process and the row of hooks.
Two preparations from Polperro in the British Museum, labelled “ Terebella
constrictor ” contain Amyhitrite scylla, Nos. 62.7.12.50, and 62.7.12.46.
Genus CXLV.—Polymnia, Malmgren, 1865.
Cephalic lobe with a large collar, and at its junction with the body a series of
eye-specks, whilst a frilled inward curve occurs at each lower edge. Second, third
and fourth segments with small lamellse. Anterior ventral shields larger than the
1 ‘ Memorie/ vol. iii, p. 169, tav. xlv, fig. 2.