Genus BOWERBANKIA, _Farre_.
_Bowerbankia_, Farre, Phil. Trans. Roy. Soc. cxxvii, p. 391 (1837).
_Bowerbankia_, Hincks, _op. cit._ p. 518.
_Zoarium_ vertical or rec.u.mbent. _Zooecia_ ovate or almost cylindrical, arranged on the stem singly, in cl.u.s.ters or in a subspiral line.
_Polypide_ with 8 or 10 tentacles.
Bowerbankia caudata, _Hincks_.
_Bowerbankia caudata_, Hincks, _op. cit._ p. 521, pl. lxxv, figs. 7, 8.
This species is easily distinguished from all others by the fact that mature zooecia have always the appearance of being fixed to the sides of a creeping, adherent stem and are produced, below the point at which they are thus fixed, into a pointed "tail."
Subsp. bengalensis, _Annandale_.
_Bowerbankia caudata_, Thornely, Rec. Ind. Mus. i, p. 196 (1907).
_Bowerbankia caudata_, Annandale, _ibid._ p. 203.
_Bowerbankia caudata_ race _bengalensis_, _id._, _ibid._ ii. p. 13 (1908).
The Indian race is only distinguished from the typical form by its greater luxuriance of growth and by the fact that the "tail" of the zooecia is often of relatively great length, sometimes equaling or exceeding the rest of the zooecium. The stem, which is divided at irregular intervals by part.i.tions, often crosses and recrosses its own course and even anastomoses, and a fur-like structure is formed in which the zooecia representing the hairs become much elongated; but upright branches are never formed. The zoarium has a greenish or greyish tinge.
TYPE in the Indian Museum.
GEOGRAPHICAL DISTRIBUTION.--_B. caudata_ subsp. _bengalensis_ is common in brackish water in the Ganges delta, where it often occurs in close a.s.sociation with _Victorella bengalensis_, and also at the south end of the Chilka Lake in the north-east of the Madras Presidency. Although it has not yet been found elsewhere, it probably occurs all round the Indian coasts.]
Division PALUDICELLINA, nov.
This division consists of two very distinct families, the species of which are easily distinguished at a glance by the fact that in one (the Paludicellidae) the zooecia are tubular, while in the other (the Hislopiidae) they are broad and flattened. The anatomical and physiological differences between the two families are important, and they are a.s.sociated together mainly on account of the method of budding by means of which their zoaria are produced.
[Ill.u.s.tration: Fig. 35.--Single zooecia of _Victorella_ and _Hislopia_ (magnified).
A, zooecium of _Victorella pavida_, Kent, with the polypide retracted (after Kraepelin).
B, zooecium of _Hislopia lacustris_, Carter (typical form from the United Provinces), with the collar completely and the tentacles partly protruded.
A=collar; B=orifice; C=tentacles; D=pharynx; E=oesophagus proper; F=gizzard; G=stomach; G"=cardiac portion of stomach; H=intestine; J=r.e.c.t.u.m; K=a.n.u.s; L=young egg; M=green cysts in gizzard; N=testes; O=ovary; O"=funiculus.
The muscles are omitted except in fig. B.]
Family PALUDICELLIDae.
PALUDICELLIDae, Allman, Mon. Fresh-Water Polyzoa, p. 113 (1857).
h.o.m.oDIaeTIDae, Kent, Q. J. Micr. Sci. x, p. 35 (1870).
VICTORELLIDae, Hincks, Brit. Marine Polyzoa, p. 558 (1880).
PALUDICELLIDeES, Jullien, Bull. Soc. zool. France, x, p. 174 (1885).
PALUDICELLIDES, Loppens, Ann. Biol. lacustre, iii, p. 170 (1908).
VICTORELLIDES, _id._, _ibid._ p. 171.
_Zoarium._ The zoarium is rec.u.mbent or erect, and is formed typically either of zooecia arising directly in cruciform formation from one another, or of zooecia joined together in similar formation with the intervention of tubules arising from their own bases. Complications often arise, however, either on account of the suppression of the lateral buds of a zooecium, so that the formation becomes linear instead of cruciform, or by the production in an irregular manner of additional tubules and buds from the upper part of the zooecia. A confused and tangled zoarium may thus be formed, the true nature of which can only be recognized by the examination of its terminal parts.
_Zooecia._ The zooecia are tubular and have a terminal or subterminal orifice, which is angulate or subangulate as seen from above. Owing to this fact, to the stiff nature of the external ectocyst, to the action of circular muscles that surround the tentacular sheath, and to the cylindrical form of the soft inverted part, the orifice, as seen from above, appears to form four flaps or valves, thus [ill.u.s.tration: sketch, similar to a cloverleaf inside a square with rounded corners].
_Polypide._ The alimentary ca.n.a.l is elongate and slender as a whole, the oesophagus (including the pharynx) being of considerable length. In _Paludicella_ and _Pottsiella_ the oesophagus opens directly into the cardiac limb of the stomach, which is distinctly constricted at its base; but in _Victorella_ the base of the oesophagus is constricted off from the remainder to form an elongate oval sac the walls of which are lined with a delicate structureless membrane. _Victorella_ may therefore be said to possess a gizzard, but the structure that must be so designated has not the function (that of crushing food) commonly a.s.sociated with the name, acting merely as a chamber for the retention of solid particles. In this genus the cardiac limb of the stomach is produced and vertical but not constricted at the base. The tentacles in most species number 8, but in _Paludicella_ there are 16.
_Resting buds._ The peculiar structures known in Europe as "hibernacula"
are only found in this family. The name hibernacula, however, is inappropriate to the only known Indian species as they are formed in this country at the approach of summer instead of, as in Europe and N.
America, at that of winter. It is best, therefore, to call them "resting buds." They consist of ma.s.ses of cells congregated at the base of the zooecia, gorged with food material and covered with a resistant h.o.r.n.y covering.
The family Paludicellidae consists of three genera which may be distinguished as follows:--
I. Orifice terminal; main axis of the zooecium vertical; zooecia separated from one another by tubules.
[A. Base of the zooecia not swollen; no advent.i.tious buds POTTSIELLA.]
B. Base of the zooecium swollen; advent.i.tious buds produced near the tip VICTORELLA, p. 194.
II. Orifice subterminal, distinctly on the dorsal surface; main axis of the zooecium horizontal (the zoarium being viewed from the dorsal surface); buds not produced at the tip of the zooecia PALUDICELLA, p. 192.
Of these three genera, _Pottsiella_ has not yet been found in India and is only known to occur in N. America. It consists of one species, _P.
erecta_ (Potts) from the neighbourhood of Philadelphia in the United States.
_Victorella_ includes four species, _V. pavida_ known from England and Germany and said to occur in Australia, _V. mulleri_ from Germany (distinguished by possessing parietal muscles at the tip of the zooecia), _V. symbiotica_ from African lakes and _V. bengalensis_ from India. These species are closely related.
_Paludicella_ is stated by Carter to have been found in Bombay, but probably what he really found was the young stage of _V. bengalensis_. A single species is known in Europe and N. America, namely _P.
ehrenbergi_, van Beneden (=_Alcyonella articulata_, Ehrenberg).
I have examined specimens of all the species of this family as yet known.
Genus 1. PALUDICELLA, _Gervais_.
_Paludicella_, Gervais, Compt. Rend. iii, p. 797 (1836).
_Paludicella_, Allman, Mon. Fresh-Water Polyzoa, p. 113 (1857).
? _Paludicella_, Carter, Ann. Nat. Hist. (3) iii, p. 333 (1859).
_Paludicella_, Jullien, Bull. Soc. zool. France, x, p. 174 (1885).