and second segments. A single pair of : branchiae ramified at their extremity and attached
to the third segment. Ex. T. cristata. -
Cuvier distinguished the Terebellids by their having tubes composed of sand and
fragments of shells, by their bodies possessing fewer rings, the mouth being surrounded
by mobile tentacles, and the neck having gills in the form of arbuscles, of which most
have three pairs. After Savigny he used these in classification, those with two pairs of
gills being the T. Phyzeliæ, and with one the T. ldaliæ.
Milne Edwards1 (1838) gave an account of the circulation in TerebeUa nebulosa,
Montagu, and T. conchilega, Sav., which for the most part agrees with modern interpretations.
He considered the anterior part of the contractile dorsal vessel a pulmonary heart
since it sent blood to the branchiæ ; whilst the ventral vessel chiefly performed arterial
functions. The contractile gills also aid in the circulation. In T. conchilega he found
that the lateral branches of the ventral vessel do not form rings on the upper surface of
the gut, but go exclusively to a vascular “ locis rete ” situated on each side of the visceral
cavity near the bases of the feet, other branches supplying the intestinal wall.
The same author3 (1844) examined the development of Terebella nebulosa, Mont.
The ova were yellowish brown and were immersed in a gelatinous mass in the tube. He
followed the various stages in the mucus, the assumption of the ovoid form, the appearance
of two eye-spots, the occurrence of the prototroch, and the perianal ring of
cilia. Then the apodous larva acquired new segments in front of the pygidium and the
segments were outlined. He noted the development of the alimentary system, and that
in two or three days the cephalic lobe was distinct, with its eyes and a median appendage,
whilst the coelomic cavity had corpuscles in its fluid. By-and-by the natatory cilia
disappeared, but the buccal and the anal region showed energetic ciliary action. The
young thus differed from the adult and conformed to the general type of the Polychæts.
They then secreted cylindrical transparent tubes, acquired additional bristles, and hooks
were developed ventrally. On the eighteenth day the cephalic plate was enlarged, the
eyes atrophied, and there were six pairs of feet. After a time a ne& cephalic appendage
was formed—filiform, long, and furnished with “ vésicules urticants,” yet no bloodvessels
had appeared. Other tentacles followed, and whilst the larval eyes had
disappeared, a number of oculiform points occupied the frontal segment, and the ventral
scutes were distinct. When the young Terebellid had about forty pairs of feet the
branchiæ appeared, simple at first, but afterwards branched, and the blood-vessels were
distinguishable. • At the length of 10 or 12 mm. ova were shed into the coelomic cavity.
All the organs soon assumed the adult character.
In Griffiths’ edition of Cuvier’s 4 Animal Kingdom ’ (1824—33) it is stated that the
female part is composed of a single median ovary occupying the whole inferior face
of the visceral cavity so far as the ninth ring, terminating behind, according to Pallas,
in a bifurcation. It is composed of a great number of oviferous grains, and has a single
opening posteriorly. The male organs consist of four pyriform vesicles placed on each
side of the anterior moiety of the ovary. They open externally by minute orifices
between the feet.
1 4 Ann. Sc. nat./ 2e sér., t. x, p. 199, pi. x, fig. 1.
2 4 Comptes Bend. l’Acad. Sc. Paris/ -p. 1411.
In Terebella conchilega, De Quatrefages1 (1844) found the cephalic ganglia elongated
fusiform, with cönnëcÉïès in the middlefMne, and givinj||éff three or four pairs of
nerves to the cirri. Thé oesophageal connectives are short and thick, and from their
anterior part a small branch with a ganglion may represent the visceral system. The
ventral chain is single in front (anterior region) with the usual ganglia. In the posterior
region the chain is double, though the ganglia are united by commissures as in Aonia
and Malacoceros.
Johnston* (1845) constituted the family Terebellid®, which he separated from the
Pectinarians and Sabellarians.
Grube (185-Splaced the Terebellid® between the Maldanid® and the Hermellid®,
a position, less convenient than subsequent investigations, proved, and like some of
his predecessors he included the Amphictenid® and Ampharetid® under the same
bead__Terebelliformia—distinguishing them by the presenc|i»f pale® in the mouthsegment.
M. Sars did much to extend our knowledge of the northern species of Terebellids
in his various papers, adding such interesting forms as TerébelUdes, Amocit; and in 1868
found the following forms at a depth of 800 fathoms, viz., Terebella artifex, TerébelUdes'
strmmi, and Ereutho smittiA
'Br. Thos. Williams (1858) examined the segmental organs in the thoracic region
of T. nebulosa and other species, one half being highly vascular, the other membranous
and excretory, the former being connected with the ovary or spermary, the latter being
the efferent . ehahnel. He held that the long glandular mass in front was a secretory
organ in connection with tube-formation. This family and the Arenicolid® were, he
stated, the only two in which the reproductive elements were shed into the body-cavity®
a statement which cannot now be made. He further observes 4 that "in the Terobell®
and Serpul®, which are oephalo-branchiate,-the anterior extremity of the great dorsal
trunk enlarges fusiformly and propels the blood directly into the branchial appendages.
In these genera therefore this vessel becomes the branchial heart; and the great ventral
trunk, into which the efferent branchial vessels empty themselves, becomes the systemic
aorta."
Malmgren (1865) grouped the Terebellacea under five sub-families, viz., Amphi-
tritea, Polycirridea, Artacamagpa, Trichobranchidea, and Canephoridea, and he gave
a useful syllabus of the genera under, each. The Amphitritea presented a truncated
cephalic lobe with numerous canaliculated tentacles arising from a musonlar lip, and
behind them numerous ocular points. Blood-vessels conspicuous;: Branchi® generally
present. Bristles capillary and winged, generally in the anterior region of the body,
sometimes throughout the entire length. Avicular or rarely pectiniform hooks on tori,
and of similar structure throughout. This author has the credit of placing the structure
and arrangement of the bristles and hooks of the group on a proper footing. His
classification is as follows:
1 Ann. So. nat.,’ 3° aér., t. xiv, pp. 368—9.
2 ' Ann. Nat. Hist./ vol* xvi, p. 447.
8 ' Vidensk.-Selak. Forhandl./ 1868 (sep. copy), p. 10,
4 'Rept. Brit. Assoo./ ]