of bivalves. The coarser tubes show large fragments of shells, half a Gardium or other
shell conspicuously projecting here and there, and the nacreous (or it may be the
purple) surface of the mussel and the nacreous surface of such as Nucidct, already
mentioned, is exposed. These fragments often slant from before backward, but with
frequent interruptions, so as to render the tube as difficult to draw by front as by rear
through the sand. All these shelly-fragments and particles of gravel would appear
to be placed and cemented in position after the thin inner lining of the tough secretion
is formed. The lining of secretion keeps the channel smooth so long as no bending
occurs. A tube with moderately, coarse grains is still translucent here and there so
as to give the annelid light, if that is of importance to it. The locality in which the
tube is situated, of course, has an influence on its structure, those from sandy regions
being fine, those from gravel or shell-gravel are coarse. Those from deep water
generally have more of the membranous and less of the shelly materials—it may be from
their scarcity. The coiled tubes situated in the valves of Mytilus modiolus present
considerable patches of membrane, and one surface is glued to the shell, the protective
structures being fragments of heart-urchins, entire green-pea urchins, spines of
sea-urchins, and heart-urchins and small shells of Dentalium. At Lochmaddy the
tubes are often composed of minute fragments of gneiss and quartz, whilst at
Connemara fragments of Lithothamnion are common, the coarser fragments being
posterior, and the finer, with Foraminifera and other minute particles, forming the
branched termination.
In some the anterior aperture has two flattened plates composed of scale-like
fragments of bivalves or of entire valves, the fimbriee being attached to the margins,
and the two plates, by the elasticity of the secretion, are closely applied except on the
issue of the annelid. Moreover, much finer fibres are sometimes attached to one end of
the flattened anterior aperture.
Occasionally the ordinary tube is again continued beyond the branching anterior
end, and a new arborescent termination constructed.
The arborescent anterior end of the tube is formed by cementing such elongated
bodies as the spines of the heart-urchin, elongated fragments of shell or gravel, which
are placed parallel to the long axis of the fibre or its branches. Moreover, where the
tubes are composed of fine grains the fibres are correspondingly delicate. In some a large
fragment of shell is utilised in the arborescent tuft, apparently for strength, or in the
case of a limpet-shell for protection. The arborescent tuft has a transversely flattened
form, and the large aperture is protected by a basal web at each side (Plate CXIX,
figs. 8 c and 8 d). Occasionally the annelid avails itself of the neighbouring branches
of zoophytes or Polyzoa. The arrangement of the branches at the anterior end of the
tube is apparently connected with the safety of the delicate tentacles and branchiae. As
the advancing tide covered the tubes at Lochmaddy a cloud of mud was thrown out by
the annelids.
Mr. Arnold Watson, who has done such excellent work by observing tubicolar forms
constructing tubes in his aquaria, was good enough to send a copy of a photograph
of a newly-constructed branched process at the end of a tube showing graceful curves of
the filaments formed of single grains of sand and minute particles of shells. Subsequent
strengthening of the filaments by larger particles renders the whole coarser and
less graceful.
After a severe storm, as, for example, on October 15th, 1863, the West Sands, at
St. Andrews, from the bridge at the Swilcan Burn outward were covered with vast
multitudes of the tubes of Lanice conchilega. They especially abounded at the lines
of mid-tide and low water, where the ebbing tide threw them into broad ridges with
intervening grooves. They ranged from the very rough to the membranous, and almost
all were empty. It was thus chiefly a loss of home, and not a loss of life. So vast were
the masses that a civic authority thought they might be utilised as manure, but their
composition gave slight basis for such a view, although they might be useful when
applied to a clayey soil.
The absence of definition in Delle Chiaje’s figures (1828 and 1841) and the brevity
of his descriptions make the diagnosis of his Amphitnte Tondi somewhat uncertain, but
it is probably the present species.
Dalyell (1853) gives an interesting account of the habits of this species in confinement,
especially in connection with the formation of its tube and the action of the
tentacles. It is for the most part nocturnal. He termed it the sand-mason.
De Quatrefages (1865) included this species under the titles of Terebella conchilega
and T. prudens.
Claparède (1868) gave the species only sixteen pairs of bristle-bundles, and considered
that Delle Chiaje’s Amphitrite Tondi was only a ripe form of this species. He found a
greenish hue present at the period of sexual maturity due to a multitude of fatty cells in
the coelom.
On May 6th, 1878, Giard communicated to the French Academy a note on an annelid
which was formerly considered as a young Terebella, and which he termed Wartelia, thus
conferring on the young stage of a Terebellid a separate title.
Cosmovici (1880), mentions two pairs of segmental organs and organs of Bojanus
in this species, one pair of the latter situated in front and the other behind the cephalic
diaphragm. In shape the segmental organs, which are separated from the organs
of Bojanus and lie behind them, are like urns with a crenate and much ciliated mouth,
and he figures the ova attached to the narrow end of the funnel whilst the inner edge of the
funnel is prolonged as a narrow process toward the nerve-cords. He held that the reproductive
elements were discharged through the funnel. The organ of Bojanus has no
external aperture. The genital glands have, he observed, a close association with the
segmental organ and its vessels. He states that he has noticed T. conchilega depositing
eggs in May at Roscoff, and the ova were very numerous. This author, therefore, is at
variance with the results of those who. have examined the structure of the nephridia in
the Polychæts, and J. T. Cunningham’s subsequent observations are more in accordance
with the actual structure.
Langerhans (1880) gives frontal outlines of the hooks, showing that anteriorly five
teeth occur above the main fang, whilst posteriorly three rows are above it, no less than
fourteen points being shown.
Marenzeller (1884) included the Terebella gigantea of Montagu1 under this species
* ‘ Linn. Trans./ vol. xii, p. 341, Tab. xi.