Capoilïlialyry i nb rthisetl es anttehreio br opdayr.t of
Three pairs
Two pail's
CBarapnilclahriyæ b arbisstelnets..
sqAuallmlyo ssut b- fruticose.
Aporbsto, rsemscaellnetr ;. Hooks
Ftharsoiculgesh oouf tc tahpei lelanrtyir eb rbiostdlyes. Branchiæ
Noe degyee so. f Abrviisctluelsa rs utrnicoi-nsei rarnud- "Pelcatintifeor..m... .................................. (Prloadrugceeladt eirnatloli pa ShBorritsa tnleds n arwroi twh. I m . I In fifteen segtmipesn stms. ooBthran- H LrapHniary j j noM »saervbeonwteselanm t.s egm. ents..
I bristies v Bi-anchii» subclaviform .
I OCnape ipllaairry. (| Inb treinst lseesg ments |l IInn sfiefvteeennte seeng smeegnmtse nts . Ramose, arbore/s Tcwenot,, gfeonremrailnlyg thar eec opnatiirgsuous transverse •|j Thsreereie. s oFnas ceiacclehs soifd e . . . IV brisotnle sse bgemgeinnnt ing -
( Fsielgifmoremnt si.n
Nicolea, Mgrn.
Pista, Mgm.
AScxiioonnei,c eM, gMmg.r n.
LLeaoenansas,a M, Mgrgnr.n . LLeapprhæaan,i aM, Mgmg.rn.
Thelepus (Leuck.).
NGeiyomttiæs,a ,M Mggmr.n .
After an interesting historical summary, De Quatrefages (1865), gives a brief account
of the structure of the Terebellidse, first investigated by Pallas, and subsequently by
Milne-Edwards, Grrube and himself. He points out the delicacy of the cutaneous tissues,
the large size of the perivisceral cavity, the contents of which enter the tentacles (his
cirri). He mentions three pairs of “ salivary glands i connected with the digestive system
anteriorly. The vascular system presents a dorsal and a ventral trunk, the latter
continued to the posterior end of the body, but the former at the junction'of the oesophagus
with the intestine abuts on a large vascular ring surrounding the alimentary canal, and
oiving origin to a slender dorsal branch, and a larger ventral trunk which extends
throughout the intestine. In the proboscidian region the superior branch furnishes trunks
to the branchiae. The blood is usually red, though Schmarda found it green in two from
Jamaica and one from Chili. The branchiae are the respiratory organs except in the
abranchiate types, where the cutaneous tissues subserve this function. The nervous
system shows a bilobed cephalic region. Anteriorly the ganglia are fused in the middle
line, but thereafter the chain is simple. The cords are separate in the posterior region.
In his classification of the family into Branchiate, Abranchiate and- Heteroterebellids,
he starts with the primary distinction of a body divided into two regions or composed of
one only, eight genera falling under the former, three under the latter, which he
distinguishes as the Heteroterebellidge. The first series (Branchiate) is divided according
as they have or have not dorsal branchiae, those having three pairs of arborescent dorsal
branchiae belonging to the genus Terebella, with two pairs to Physalia, and with one pair
to ldalia. Of the others TerebelLides has pectinate median branchiae; whereas simple
cirriform buccal branchiae characterised Phenacia, and pinnate buccal branchiae the
Sabellidce. On the other hand cirriform and pinnate branchiae are both present in Isolda.
The last of this series is Apneumea with no dorsal branchiae, and which therefore forms
the second tribe (Abranchiata). The third tribe, as mentioned, has the body composed of
a single region, and two of the genera have arborescent dorsal branchiae, viz., Hetero-
terebella with three pairs, and Heteroph/yseLia with two pairs, ffeterophenacia, again, has
cirriform branghiæ. This author therefore made a useful classification for the period, but
it lacked the precision and breadth which the study bf «other structural features subsequently
gave, and he iiiëluded: the Ampharetidæ in the family instead of separating them.
Dr. Johnston (1*8,66) made the Terebellidæ his fifteenth family out of a total number
of sixteen, but his description includes the characters of the Amphictenidæ as well as
those of t | | Terebellidæ. Accordingly fie presence or absenete|j|a front armed with a
row of stiff brisüSâ condtïjuted his main divisions. The Terebellidæ were arranged in
three groups, the first haying three pairs of branchiæ, the-jspcond two pairs, and the third
one pair—a classification more or less on the linescof De Quatrefages.
H H M Vaillant1 (186:5), who had studied, an imperfect exam plêb|| Pplycirrid, thought
that the tentacles indicated a series of buds. The error was noted at the timo, and Ch.
Gravier* has sincefully explained the misinterpretation.
Claparède!,(186,8) divided this family iS ) two tribes, # . , Branchiate and Abranchiate,
and he made special remarks about the tori mémgeri, which he ranged under five heads
according as their hooM pointed forw ard« rangée progressive | | backward (“ r e tr o gressive”),
alternated (“r. alterne”), similar to the last but wider apart (“r. engrenantes”),
and lastly an anterior and posterior row with opposite, pointstppnnected by. a curved series
at one endi(“ r. parabolique”). He found young forms at Maples easily discriminated by
this method. He also alludes to the tendinous processes attaohed to the hif^s under the
title “ spies'de soutien ” or “ soies-tendoh* in the posterior region. In his later publication
(187t(|: % . author corrects A„TGosta and others, who insistfl bn the presefiMof
vessels in the tentacles of this family. Only the ccelomic fluid penetrates into these organs.
In Ciapariido’s posthumous work on the structure of the sedentary Annelid- Efcj-: 11
many interesting remarks occur on the Terebellids, especiallylpjconnectionwith TerMla]
fiemoia, a few of which may be summarised. He .lays great trtmsKaz» the supporting
functions of his clypeal tissue in Terebellids. It not only furnishes, the external shield-
like thickenings in the mid-ventral region, but passes internally and forms a .jpap. m the
pefivisceral chamber supporting the nerve-trunk and yessèls. The connective tissue,
again, is amorphous, with nuclei. The new hooks are formed at one extremity of the
tor,vis only, and the torus is hypodermic. He states that the dorsal longitudinal muscles
are united in the Terebellids and that there is a lateral dorsal muscle. The circular
muscle forms only an isolated cordon in each segment in the thoracic region, and by this
he refers to the lateral region below the bristles ; yet in bis figure;, (Plate IX, fig. ?); it is
seen that he really means the circular or transverse fibres.outside the nerve-cord. He
considers tko oblique muscles as of minor importance-:in the Terebellidss y»t they are
largely developed in sedentary annelids. The nuclei |||th e muscular fibres are external
as in TOhlei goccohelæotms, is- divided into two Chambers by a longitudinal median mesentery
enclosing the dorsal and the ventral vessels. Moreover, no communication exists between
the perivisceral chamber in Polychæts and the. exterior as in Dtmlffeg! A large part
of the body in Terebellids is devoid of dissepiments. In certain ffirms a diaphragm
‘ ‘Ann. Sc. nat.,’ t. i;i, pp. 242—260, pi, iii.
1 ‘ Ball. Sq0^Philomath. Pari»? 1906, pp. 1—14, with text-fig».