9. Plumatella Allmani, Hancock.

Fig. 16.*

Specific character.-Cœnocium adherent, creeping; cells claviform, keeled. Tentacula forty-two; calyx distinctly festooned. Statoblasts elongated.

SYNONYM.-1850. Plumatella Allmani. Hancock, Ann. Nat. Hist., 2d series, vol. v, p. 200, pl. 5, figs. 3-5. (Original figures.)

Iconography-Original figures by Hancock.

HABITAT.-Lakes, attached to the under side of stones.

LOCALITY.-Bromley Lough, Northumberland, rather abundant. Hancock.

I have not met with this Polyzoon. Mr. Hancock, who discovered it along with several other species in Bromley Lough, in the county of Northumberland, describes it as follows: Polypidom attached to the under side of stones, adhering throughout; membranous, opaque, yellowish-brown, slightly branched, extending in patches sometimes three or four inches wide, the patches being made up of several polypidoms; the branches composed apparently of a series of tubular cells, tapering to their origin, and attached for more than half their length; the enlarged extremity being free and bending upwards, inclines a little to one side, and is occasionally bifid, forming two cells; an obtuse ridge or keel extends the entire length of the cell, increasing imperceptibly in thickness upwards; orifice somewhat constricted, the walls immediately below being pellucid and suddenly dilating, become abruptly opaque and thickly covered for some distance downwards with agglutinated sand. Tentacles forty-two in number, slightly tinged with yellow, the colour best seen when they are formed into a compact bundle; membrane at their base distinct, scalloped, the point being prolonged a little

*Figure copied from Hancock.

up the tentacles. Egg (statoblast) black, long, oval; sides nearly parallel; margins pellucid, yellow, sharp, broad, and reticulated.

"This species was procured rather abundantly in Bromley Lough, and does not appear to vary much. At first sight, large patches of it have the appearance of being formed of a single polypidom; but on close examination are found to be composed of many, and rarely to number more than six or eight, cells in each. The commencement of each polypidom has the black envelope of the originating egg (statoblast) adherent.'

Plumatella Allmani certainly comes very close to P. emarginata and P. diffusa; it is, however, distinguished from both by its cells being claviform, while they are cylindrical in P. emarginata, and keg-shaped towards the orifice in P. diffusa. Mr. Hancock describes the cœnœcium as keeled, but makes no allusion to the oblique or notch-like termination of the earthy deposit in the ectocyst, which is so distinct a character in P. emarginata, P. diffusa, and some other species; and yet from the very expressive figures of Mr. Hancock, I am inclined to believe in the existence of this character also in the present species.

10. Plumatella elegans, Allman. Pl. VIII, figs. 6-10.

Specific character.-Conocium adherent, creeping, cells of uniform diameter; with a furrow and keel. Calyx but slightly festooned. Statoblasts broad.

SYNONYM.-1850. Plumatella elegans. Allman, British Association Report, 1850.

Iconography.-No published figure.

HABITAT. On the under side of floating leaves in still water. Avoiding the light.

LOCALITY.-Millpond, Bandon Distillery, county of Cork, attached to the under surface of the leaves of Potomogeton natans.

I have as yet met with P. elegans only in one locality, and there it was by no means abundant. It occurred upon the under surface of the leaves of Potomogeton natans in small irregular patches, formed by a somewhat sinuous, branched, closely adherent tube. The ectocyst is brown, sabellose in its texture, and with a well-marked furrow, which passes below into a keel, and terminates near the orifice in a broad notch-like space. Transverse septa may be distinctly seen intersecting most of the cells near their origin. The polypides are small, and the calyciform membrane exhibits scarcely a trace of festooning. The statoblasts are elliptical, with a widely overlapping annulus; they are narrower than those of P. repens, but wider than the ova of P. emarginata, and present no tendency to the bean-shaped figure of the latter.

It was during the month of August that I met with this species.

11. Plumatella Dumortieri, Allman. Pl. VIII, figs. 1—5.

Specific character.-Conocium adherent, irregularly branched; cells somewhat dilated towards the orifices, with a furrow carinated. Tentacula about fifty; festooning of calyx deep and distinct. Statoblasts broad.

SYNONYM.-1850. Plumatella Dumortieri. Allman, British Association Report.

Iconography.-No published figure.

HABITAT.-On submerged plants in still water.

LOCALITY. In a pond at Crix, in the county of Essex, the property of Samuel Shaen, Esq. G. J. A.

This species has as yet been met with only in one locality, where, though I found several specimens, it was far from being abundant. It presented a small, irregularly branched cœnœcium, closely adherent to the submerged portions of Potomogeton natans and other aquatic plants. The ectocyst is yellowish-brown, becoming, as in all the furrowed species with which we are as yet acquainted, lighter coloured towards the extremity of the ramuli, and then assuming the thin transparent condition, which it retains as far as the orifice. This transparent portion is frequently dotted with minute brown points. The calyciform membrane of the polypide is nearly as deeply festooned as in Fredericella, and the statoblasts are broadly elliptical, resembling those of P. repens. I met with it in the month of July.

I have given to this species the name of M. Dumortier, a naturalist to whom we are indebted for some of the most valuable information we possess on the fresh-water Polyzoa.

11. Plumatella jugalis, Allman. Pl. VI, figs. 1, 2.

Specific character.-Cœnocium adherent, consisting of two series of branches connected by a common tube, and extending in opposite directions; cells of uniform diameter, with a furrow which passes below into a keel. Tentacula about forty; calyx with shallow festoons. Statoblasts not known.

SYNONYM.-1850. Plumatella jugalis. Allman, British Association Report.

Iconography.-No published figure.

HABITAT.-On submerged plants in still water.

LOCALITY.-Canal near Little Baddow, Essex. G. J. A.

P. jugalis is a small species and occurs, rather abundantly in the sluggish waters of the Chelmer Canal, attached to the petioles and under surface of the leaves of Nymphæa alba. It is throughout closely adherent to the surface on which it grows, and is very remarkable by its mode of development in two distinct groups of branches, which are united to one another by a simple connecting tube, from which they extend in two opposite directions. The ectocyst is brown, becoming lighter towards the extremities of the branches, and finally extending as a delicate transparent and colourless membrane to the margin of the orifice; this transparent portion being, as in other furrowed species, withdrawn into the more opaque portion of the tube during extreme retraction. Most of the branches are intersected near their origin by very distinct septa, which are visible through the walls of the tube. I could find no statoblasts in any of the specimens I examined.

In its peculiar mode of development in two groups of tubes, P. jugalis presents a striking resemblance to Alcyonella flabellum; from the latter animal, however, it is at once distinguished by its narrow, widely diverging branches never contracting the slightest adhesion to one

another.

I have as yet met with this species in but one locality, though its striking physiognomy could scarcely allow of its being overlooked.

The Plumatella nitida, Leidy (Proc. Acad. Nat. Sci. of Philadelphia,' vol. v, p. 321), I cannot think entitled to rank as a distinct species. With the exception of the number of tentacula, which are described as being only forty-two, there is no character in which P. nitida does not entirely agree with P. repens, and this character by itself can scarcely be considered of sufficient importance to separate the two forms.

110

Genus VI. FREDERICELLA, Gervais, 1838.

Name.-In honour of Frederick Cuvier.

In 1774 Blumenbach gave the name of Tubularia sultana to a little fresh-water Polyzoon which he found in the neighbourhood of Göttingen, and which differed from all the then known fresh-water species in having the tentacula disposed in a circle instead of forming a crescent. This circular disposition of the tentacula, which at once distinguishes Blumenbach's animal from all the other fresh-water species except Paludicella, was properly considered by M. Gervais to be of sufficient importance to cause the Tubularia sultana to take the rank of a distinct genus, and he has accordingly assumed it as the type of his genus Fredericella.

Though the tentacular crown, however, may at first appear quite similar in its form to that of Paludicella, a careful examination will detect in the lophophore a deviation from the orbicular condition presented by this part in the latter, and the bi-laterality of the lophophore in Fredericella is still further maintained by the presence of the epistome, which is altogether absent in Paludicella. The epistome and calyciform membrane are, indeed, as well developed in Fredericella as in the species with crescentic lophophores, while Paludicella, the only genus with a truly orbicular lophophore, is also the only one in which the epistome and membrane are absent. The whole structure, moreover, of Fredericella is quite in accordance with that of the species with crescentic lophophores, and differs in many important particulars from the structure of Paludicella, so that notwithstanding the circular disposition of the tentacula the true affinities of the genus are with Plumatella rather than Paludicella

Generic character.-Cœnocium confervoid, composed of a membrano-corneous branched tube, with the branches distinct from one another and terminated by the orifices. Lophophore nearly circular; tentacular crown campanulate. Statoblasts bean-shaped, destitute of annulus and spines.

Species unica.* F. sultana, Blumenbach. Pl. IX.

Specific character.-The same as that of the genus.

SYNONYMS.-1777. Tubularia sultana. Blumenbach, Handbuch der Naturgeschichte. (Original figure.)

1789. Tubularia sultana. Gmelin, Linn. Syst. Nat., p. 3835.

* In my Synopsis of Fresh-water Zoophytes, published in the Annals of Natural History,' 1844, I have described as a distinct species, with the specific name dilatata, a Fredericella in which the branches become dilated towards the extremities; subsequent investigations, however, have led me to look upon the F. dilatata of that publication as a merely accidental variation of F. sultana, and the species must accordingly be suppressed.