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1806. Tubularia sultana. Turton, Linn. Syst. Nat., vol. iv, p. 669.
1816. Naisa sultana. Lamouroux, Pol. flex., p. 224.
1828. Plumatella gelatinosa. Fleming, Brit. Anim.
1830. Difflugia proteiformis. Meyen, Isis, 1830, p. 187.
1834. Difflugia protæiformis. Meyen, Nov, Act. Acad. Cæs. Leop., vol. xvi,

Suppl.
1836. Plumatella sultana. Dumortier, Mém. sur les Pol. comp. fluv., p. 22.
1838. Plumatella sultana. Johnston, Brit. Zooph., 1st edit., p. 323.
1838. Fredericella sultana. Gervais, Bull. Soc. Philomat.
1839. Fredericella. Van Beneden, Bull. Ac. Brux., tom, vi, 2de partie, p. 277, fig. 2.

(Original figure.) 1839. Fredericella sultana. Gervais, Ann. Franç. et Etrang. d’Anat., tom. iii,

p. 136.

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1840. Fredericella sultana. Gervais, Dict. Sci. Nat., Suppl., vol. i, Pl. Suppl.,

Pol. Fluv. (Original figures.)
1813. Fredericella sultana. Thompson, Rep. Brit. Assoc., p. 285.
1844. Fredericella sultana.

Allman, Ann. Nat. Hist., vol. xiii, p. 331.
1844. Fredericella dilatata.
1844. Fredericella sultana. Allman, Proc. R. I. Acad., No. 44. .
1847. Fredericella sultana Johnston, Brit. Zooph., 2d edit., p. 405.
1848. Fredericella sultana. Van Beneden, Recherches sur les Bryoz. fluv. de Belg.,

p. 25, Mém. de l'Acad. Roy. de Belg. 1848. Fredericella sultana. Dumortier et Van Beneden, Hist. Nat. des Pol. Comp.

d'eau douce, Mém. servant de Complément au tome xvi des Mém. de

l'Acad. Roy. de Brux. (Original figures.) 1850. Fredericella sultana. Hancock, Ann. Nat. Hist., 2d series, vol. v, p. 173,

pl. 2, figs. 1, 4, and 6, and pl. 3, fig. 1. (Original figures.)

Iconography.— The original figures are those of Blumenbach, Van Beneden (Bul. Ac. Brux.), Van Beneden (Mém. de l'Acad. Brux.), Gervais, and Hancock. There is also an original figure apparently referable to this species, though unaccompanied by a name, illustrating a paper by Mr. Varley in the ‘Lond. Phys. Journal,' No. 2, 1844.

HABITAT.-On submerged stones and the stems and leaves of aquatic plants, in still water and moderately rapid rivulets. Preferring the shade.

LOCALITIES.British : Generally distributed through England, Ireland, and Scotland ; abundant in the Regent Canal, London; in the Grand Canal, Dublin ; and in the Union Canal, Edinburgh. G. J. A.Northumberland Lakes. Mr. Hancock. .

Foreign : In a small lake called the Roth See, near the town of Lucerne; in Lago di Mezzola, Northern Italy; in the Canal du Midi, near Toulouse. G. J. A.-Germany. Blumenbach.—Near Paris. Gervais.—Belgium. Dumortier and Van Beneden.

F. sultana is one of the most widely distributed of the fresh-water Polyzoa; I have met with it abundantly in England, Scotland, and Ireland. It occurs in rather confused tufts attached to submerged plants, stones, &c. The conæcium is partly free, partly adherent, the

adherent portion frequently extending over several inches, and sending off numerous free subdivided branches of an inch or more in height. The ectocyst is brown, membranocorneous, opaque, with a slightly prominent keel running along each branch, but without any slit-like furrow. At the origin of the branches there is frequently found a more or less perfect septum. The tentacula are about twenty-four in number, constituting when the polypide is exserted a campanulate crown of great elegance.

The statoblasts are somewhat kidney-shaped or bean-shaped, with the annulus obsolete. They are small and seem to be but sparingly produced, a circumstance in which this animal differs strikingly from several species of Alcyonella and Plumatella, in which the tubes at the proper season are constantly found loaded with statoblasts in the greatest profusion.

The close resemblance of the bushy cænæcium of this species to that of Plumatella fruticosa has been already mentioned, indeed I have no doubt of the one having been frequently mistaken for the other.

I have met with F. sultana during the whole of the spring, summer, and autumn months, both in standing water and rivers, generally avoiding direct exposure to the daylight, though not so decidedly a lover of obscurity as several other species of fresh-water Polyzoa. The tentacular plume is even to the naked eye an object of extreme elegance, and we can easily participate in the feelings which must have actuated Blumenbach when he bestowed on this little animal the imperial designation it has since borne.

tion it has since borne. It can be kept alive and healthy in a phial of pure water, and when undisturbed the polypides will readily issue from their cells and display their plumy crowns. A large branch thus studded with the campanulate crests of the polypides is an object which in elegance can hardly be surpassed, and with these strange, sentient flowers instantly retreating on the approach of danger, and when all is once more quiet again coming forward in their beauty, presents a spectacle not easily forgotten.

PALUDICELLIDÆ.

Genus VIII. PALUDICELLA, Gervais, 1836.

Name.-A diminutive noun, formed from palus, standing water.

In the number of the 'Symbolæ Physicæ,' published in 1831, Ehrenberg described under the name of Alcyonella articulata, a fresh-water Polyzoon which he discovered in the neighbourhood of Berlin. M. Gervais shortly afterwards, having discovered near Paris an animal which agreed with Ehrenberg's description, saw the necessity of separating it from Alcyonella and placing it in a distinct genus, which he named Paludicella. About the same time Ehrenberg's animal was detected in the neighbourhood of Louvain by M. Van Beneden, and in Lough Erne, in Ireland, by Mr. William Thompson, of Belfast, who was thus the first to add this interesting Polyzoon to the Fauna of the British Isles.

Paludicella is one of the best marked of all the genera of fresh-water Polyzoa ; its perfectly orbicular lophophore, with the absence of epistome and calyx, and its strikingly articulated cænæcium, formed of regular claviform cells, all separated from one another by complete septa, together with several peculiarities in its internal structure already described, remove it by a well-marked interval from the other genera of the present monograph, and approximate it to certain marine representations of the class. The genus consists as yet of but a single species.

Generic character.-Cænæcium membrano-corneous, branched; branches composed of a series of claviform cells placed end to end and separated from one another by complete septa ; orifices tubular, lateral, placed near the wide extremity of each cell. Lophophore orbicular, no epistome or calyx. Statoblasts not observed.

Species unica. Paludicella Ehrenbergi, Van Beneden.

Pl. X.

Specific character.—The same as those of the genus.

SYNONYMS.—1831. Alcyonella articulata. Ehrenberg, Symb. Phys. Evert., Dec. 1, Pol., fol. a.

1832. Alcyonella diaphana. Nordmann, Mikrograph. Beiträge, vol. ii., p. 75.
1836. Paludicella articulata. Gervais, Comptes Rend.
1837. Paludicella. Gervais, Ann. Sc. Nat., 2d series, tom. vii, p. 80.
1839. Paludicella articulata. Gervais, Ann. Franç. et Etrang. d'Anat., tom. iii, p. 75.
1839. Paludicella. Van Beneden, Bull. Ac. Brux., tom. vi, 2d part, p. 278, fig. 1.

(Original figure.)
1840. Paludicelle articulée. Gervais, Dict. Sc. Nat., Suppl., vol. i, pl. 1, Pol. Fluv.,

fig. 6. (Original figure.) 1842. Paludicella articulata. Allman, On the Muscular Syst. of Palud., &c., Roy. Irish Acad., No. 38, with a plate. (Original figure.)

1813. Paludicella articulata. Thompson, Rep. Brit. Assoc., p. 285.
1844. Paludicella articulata. Allmann, Ann. Nat. Hist., vol. xiii, p. 331.
1817. Paludicella articulata. Johnston, Brit. Zooph., 2d edit., p. 405, fig. 77,

p. 406. (Original figure.)
1818. Paludicella Ehrenbergi. Van Beneden, Recherches sur les Bryoz. fluv. de

Belg., p. 27, Mém. de l'Acad. Roy. de Belg. 1848. Paludicella Ehrenbergi. Dumortier et Van Beneden, Hist. Nat. des Pol.

Comp. d'eau douce, Mém. servant de Complément au tome xvi des Mém.

de l'Acad. Roy. de Brux. (Original figures.) 1850. Paludicella procumbens ? Hancock, Ann. Nat. Hist., 2d series, vol. v, p. 201,

pl. 5, figs. 1, 2, and pl. 4. (Original figures.) 1851. Paludicella elongata ? Leidy, Proc. Acad. Nat. Sci. of Philadelphia, vol. v,

p. 321. (Original figure.)

Iconography. The original figures are those of Van Beneden (Bul. Ac. Brux.), Van Beneden (Mém. de l'Ac. Brux.), Gervais, Allman, Johnston, Hancock, and Leidy.

Habitat.-On submerged stones in still and slowly running water. Eminently lightshunning

LOCALITIES.British : Regent Canal, London ; Chelmer Canal, Essex ; Grand Canal, Dublin ; Union Canal, Edinburgh. G. J. A.-Lough Erne, Ireland. Mr. T m. Thompson.Bromley Lough, Northumberland. Mr. Hancock.

Foreign : Lake of Lucerne, Lake of Zurich, Lago di Como, and Lago di Lugano. G. J. A. ---Near Paris. Gervais.—Belgium. Dumortier and Van Beneden.— Prussia. Ehrenberg:Near West Point, in the United States ; abundant. Prof. Bailey.

The specific name articulata, originally applied to this species by Ehrenberg, was sufficiently significant, so long as the animal was described as a species of Alcyonella ; it is now, however, quite inapplicable, for it possesses no specific meaning whatever, being expressive of one of the most striking characters on which the genus formed for it has been founded. I, therefore, entirely agree with M. Van Beneden, in admitting the necessity of changing the original specific name, and willingly adopt that of Ehrenbergi, proposed for it hy the learned Belgian naturalist in honour of its discoverer.

P. Ehrenbergi is very widely distributed, and we can scarcely account for its having so long escaped notice, except by supposing that its resemblance to some of the confervoid algæ caused it to be overlooked. The cænæcium is partly free, partly adherent. The adherent portion extends over the under surface of stones as a branched confervoid growth, the branches being given off either opposite to one another in pairs, or else singly, the development of the opposite branches being in the latter case suppressed. Besides the portion which thus continues closely adherent to the supporting surface, numerous branches remain quite free, growing in luxurious specimens frequently to the length of two inches, and being themselves ramified in a manner quite similar to what occurs in the adherent portion.

The structure of both adherent and free portion is similar, every branch consisting of a series of symmetrical clavate cells, each of which is attached by its narrow extremity to the wide extremity of the cell below it, from which its cavity is separated by a perfectly formed

septum, visible through the transparent walls of the cell; the entire cænæcium thus presents a very striking and elegant concatenated appearance. The orifices are unilateral, and are placed at the extremity of little tubes, which project obliquely forward from the side of the cell near its wide end. The branches are given off at nearly right angles from the wide part of the cell, one at each side of the tubular orifice, and are thus (unless when the suppression of one of them takes place) situated in pairs one opposite to the other, with the tubular orifice between them.

The ectocyst is a pellucid membrano-corneous tunic, nearly colourless in young specimens, but acquiring a dark brown colour by age.

The polypide has but sixteen tentacula, springing from the margin of the orbicular lophophore, in a perfectly infundibulate crown.

Van Beneden* describes the occurrence of what he terms “hybernacula,” in Paludicella Ehrenbergi. These hybernacula are gemmæ, which, under the influence of a favorable temperature, would have grown into the ordinary lateral branches of the Polyzoon, but which towards the commencement of winter acquire a conical form, and then become for a while arrested in their development. In this state, surrounded by a firm membrane of a blackishgray colour, they continue until the following spring, when the investing membrane splits to allow of the elongation of the branch. In no instance have I witnessed the hybernacula in the specimens of Paludicella collected in Britain.

P. Ehrenbergi is an exceedingly timid little animal, and a specimen may be for hours under observation before the polypides will venture to issue from their cells, and then it is often for only a few seconds at a time, that they will continue visible. It is eminently a lover of obscurity, being only found in such situations as are not exposed to the direct influence of daylight; the most luxuriant specimens I have met occurred under the arches of viaducts on the Grand Canal, near Dublin; and in similar situations elsewhere, where the constant obscurity in which they live is never interrupted by a single ray of direct daylight.

The species occur all through the year in still and slowly running water, but is most abundant during the summer and autumn.

After a careful consideration of the animal described by Mr. Hancockt under the name of P. procumbens, I have been unable to agree with this naturalist in considering it a distinct species. The main character on which Mr. Hancock relies, is the supposed smaller number of tentacula in his species, a belief to which he was naturally lead in consequence of the figure of P. Ehrenbergi given by me in the ‘Proceedings of the Royal Irish Academy, 1843,' having been erroneously engraved with twenty-six tentacula. Mr. Hancock also relies on the less densely and luxuriantly branched condition of his specimens, and on a smaller size and difference of colour in the cells, as grounds for distinction, but I believe these to be characters

* Dumortier and Van Beneden, “Hist. Nat. des Pol. Com. d'eau douce, Mém. servant de Complément au tome xvi des Mém. de l'Acad. Roy. Bruxelles.'

† Hancock, in ‘Ann. Nat. Hist.,' 2d series, vol. v, p. 201.

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