cirrus or tentacle is crenulate, with a broad base, which tapers by-and-by to a long
slender process with a slightly bulbous tip. In structure this shows externally the
cuticle and hypoderm with fibrillation, whilst internally it has granules of various
sizes probably hypodermic. It may be penetrated by the perivisceral fluid. In
life this and the anterior cirrus or tentacle move a little to and fro, or the tips are
coiled and waved. When the animal is killed in formaline the pharynx (proboscis)
occasionally protrudes as a dark mass at the upper and median region of the tentacles
(Arnold Watson).
An interesting feature in the oral region is the presence of the nuchal organs, as
demonstrated by Arnold Watson (Plate CXXXVI, fig. 21). These are frilled or folded
organs with dark-brown edges situated on each side of the pale tentacles, lying, as it were,
midway between these and the large papilla posterior to the long lateral cirrus. “ The
anterior and posterior lobes of the organ are directed (when viewed from the ventral
surface) upward so as more or less to face each other, and the small lateral (inner) lobes
are also bent upward (Arnold Watson). Considerable variation occurs in the appearance
from the simple condition in which they form erect plates with ventral face to ventral
face to the complicated structure. The lateral lobes are only found on the inner side,
i. 6. nearest the mouth, not at both sides of the organ. The margin of the lobes is
generally rounded, swollen, and varies in colour from dark grey to dark brown in contrast
with the opaque or sometimes semitransparent white of the rest of the organ, which is
always exposed—that is, above the general surface (Watson).
The tentacles form a dense mass, each marked by a longitudinal groove, the red
blood-vessel running in the middle line, the blood now flowing distally and again proxi-
mally in the same vessel. They are mobile organs, and undergo constant contractions
and elongations, the tip being often clavate or spatulate. The grooved surface of the
tentacle is minutely tubei*culated toward the tip, probably in connection with its .tactile
functions in building the tube; indeed such may perform the part of minute suckers.
The blood seems to flow to the tip of the organ, which becomes deep red, remains there
for a little, and then is sent backward. A single blood-vessel apparently with similar
action occurs in the long cirri.
The body is from 1^ to 2 inches in length, gently tapered to a comparatively broad tail,
which has the anal appendix passing off at an angle posteriorly. It is rounded dorsally,
flattened and somewhat grooved ventrally,- whilst laterally are, from front to rear, the
branchim immediately behind the long cirrus, a segment without bristles, and fifteen
bristle-tufts with lamellm for the hooks from the fourth bristle-tuft backward, or twelve in all.T
he general hue of the dorsum is brownish pink, the dorsal blood-vessel and the gills
being deep red. The first three body-segments have numerous brown specks (eyes ?) on
their posterior edges. The tentacles are dull pinkish in mass. The caudal process is
slightly yellowish. The intestine shines through the translucent iridescent skin as pale
brownish, and a large blood-vessel is attached to it dorsally, below the more slender median
dorsal trunk. This large trunk appears to end in the deep opaque reddish mass below
the median fillet of the second bristled segment. The median dorsal (superficial) trunk
commences at the tail, whereas the larger and deeper trunk on the gut appears about the
third hook-lamella posteriorly and the blood comes from below. The former contracts
from behind forward, squeezing the vessel into a pale thread. The skin is minutely
reticulated with red capillaries, and two large lateral trunks are seen on the ventral
surface. The first two ventral ridges have a series of brownish-red grains scattered on
their posterior surfaces. On the ventral surface is a lateral trunk on each side which
carries the blood backward. The caudal process has pale papillae along its sides.
In life the bright red branchiae are most- sensitive organs, now being gently extended
so as to expose each lamella separately to the water, and again abruptly contracted into a
mass. They are usually two in number, though occasionally the posterior on one side is
absent. The anterior lies immediately behind the long lateral cirrus and has the form of
a coiled process placed transversely, to which are attached many membranous leaf-like
plates which gradually diminish in size toward the tip, the whole somewhat resembling
the antenna of a lamellicorn beetle or the scorpioid cyme of Forget-me-not, or Borage,
With the leaflets crowded so thickly, the coiling of the axis and the diminution of the
lamellge at the tip present special advantages for aeration. The second branchia arises
from the dorsal edge of the segment-ridge behind the former, and its structure is the
same. The organs are firmly attached to the skin, and in softened examples are removed
with it.
' Cement-glands with muscles occur in the body (not the coelom) at the sides of four
segments, with a duct which opens near the first branchia (Hessle).1
Dorsally segmentation is less evident, but on the ventral surface the median and
lateral ridges give more definition in this respect. Aflat papilla, from which a ridge
and groove run to the mouth, lies within the long cirrus behind the veil. Then a median
fold behind the mouth is continued laterally to the first branchia. This is followed by
another median elevation or a boss with a ridge on each side to the second branchia.
The parts, however, vary much according to the degree ‘of contraction or extension, the
first-mentioned median fold in extension becoming a boss, in front of which a groove with
a fillet at each side passes to the mouth. Behind the second branchial ridge is a distinct
and longer one on each side of a median elevation, and terminating laterally in the first
bristle-papilla. The bristle-tufts are directed upward and backward, commencing with
three smaller tufts, the first two of which spring from the outer ends of ventral ridges
connected with median elevations, whilst the third has only a lateral lamella. No hooks
occur on these anterior feet. The fourth foot presents a large lamella and stronger
bristles, and the five or six following have also strong bristles, after which they diminish
to the last, which is minute—that is, not half the size of the first tuft. The structure of
all these tufts of somewhat brittle bristles is the same, though the anterior and especially
the posterior show certain modifications. Each has two kinds of stout bristles, viz.,
(1) that in which after widening a little above the base the strong shaft tapers gradually
to a somewhat rigid, sharp tip (Plate CXXIV, fig. 3 c), and (2) a shorter series in which
the stout shaft tapers to the commencement of the translucent terminal portion in which
a rudimentary double wing appears, and then it dilates into a flattened spear-head tapered
to a fine point (Plate CXXIV, fig. 3 b). The broad, flattened tip is marked by fine strife
directed distally. The serrations are large at the base of the terminal region, rapidly
1 ‘ Zool. Bidx*. Uppsala/ p. 52.