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amended in accordance with the author's personal experience. Without exception the material furnishing these descriptions was obtained from a pond of moderate dimensions on the estate of Thomas Randle Bennett, Esq., of Wentworth House, Stoke Newington.

CODOSIGA, Jas. Clark (revised). Bodies of animalcules ovate, one or a number seated at the termination of a fixed, slender, unretractile, simple or branching pedicle ; the anterior and distal portion bearing a membranous, infundibular, retractile collar; the single attenuate, flexible flagellum originating from the centre of the area which it circumscribes. Contractile vesicles conspicuous, one or more in number. Increasing by longitudinal fission.

Codosiga pulcherrima, Jas. Clk. (revised), Pl. CV., Figs. 6, 7.

Animalcules from one to as many as eight or nine in number, attached to the primary pedicle through the medium of very short secondary ones; surface of the body smooth, length of the same, exclusive of the collar, too mm. (7000 Eng. inch), breadth ndo mm.; length of the primary pedicle, four or more times that of the body, of the secondary ones about half its diameter. Contractile vesicles conspicuous, two or more in number.

Hab. Fresh water, attached to Myriophyllum and Conferva. Pennsylvania, U.S., Jas. Clark. Stoke Newington, London, W. S. K.

Codosiga echinata, n. sp., Pl. CV., Figs. 1, 2. Similar to C. pulcherrima, but the individual animalcules having the surface of their body beneath the collar beset with verticels of evenly-disposed stylate processes. Length of the body too mm., breadth dy mm.

Hab. Fresh water, on Myriophyllum and Conferva. Stoke Newington, London, W. S. K.

Codosiga umbellata, n. sp., Pl. CV., Figs. 3, 4, 5. Bodies of animalcules similar in structure to those of C. pulcherrimus, but of double the length (60 mm.) and more elongate outline, seated in groups at the terminations of a rigid tripartite, bi-tripartite, or occasionally quadri-partite, branching pedicle.

Hab. Fresh water, on Myriophyllum and Conferva. Stoke Newington, London, W. S. K.

SALPINGÆCA, Jas. Clk. (revised). Animalcules inhabiting a transparent lorica or sheath, the anterior portion of the body provided with a membranous retractile collar and bearing a single attenuate flexible flagellum. Lorica attached, sessile or pedunculate. Contractile vesicles conspicuous, one or more in number. Salpingæca gracilis, Jas. Clk. (revised), Pl. CV.,

Figs. 9, 10, 11, 12. Lorica cylindrical, solitary or in groups; expanding anteriorly, attenuate, in the form of an elongate hollow peduncle, or abruptly truncate posteriorly. Bodies of animalcules cylindrical, rounded at the two extremities. Average length of lorica to z mm., breadth Ibo mm., animalcules occupying one-third to one-half the length of its internal cavity.

Hab. Fresh water. Pennsylvania, U.S., Jas. Clk. Stoke Newington, London, on Conferva, W. S. K. Salpingæca amphoridium, Jas. Clk. (revised), Pl. CV.,

Figs. 13, 14. Lorica flask-shaped, having an inflated posterior portion and an attenuate narrow neck, sessile, or attached by a short pedicle. Body of irregular form, adapting itself to the outline of the lorica. Length of the lorica rio mm., breadth of the expanded base lo mm.

Hab. Fresh water, attached to Conferva. Pennsylvania, U.S., Jas. Clk. Stoke Newington, London, W. S. K.

BICOSÆCA, Jas. Clk. (revised). Body enclosed within an ovate membranous lorica or sheath, to the bottom of which it is attached through the medium of a contractile ligament; no collar; one or two flagelliform appendages originating from the anterior extremity. Lorica usually pedunculate. Contractile vesicles one or more in number.

Bicosæca lacustris, Jas. Clk. (revised), Pl. CV., Figs. 15, 16.

Lorica elongate oval, narrowing at the anterior extremity, attached by a short pedicle. Body rounded posteriorly, rostrate anteriorly and bearing a single flagellum originating excentrically, curved and rigid in extension and a shorter stylate appendage. Length of lorica Tšo mm., breadth ato mm.; body occupying onethird to two-thirds of its internal cavity. Contractile vesicles two in number.

Hab. Fresh water, on Conferva. Pennsylvania, U.S., Jas. Clk. Stoke Newington, London, W. S. K.

Bicosæca socialis, n. sp., Pl. CV., Fig. 17. Lorica elongate oval, half as long again as that of B. lacustris ; pedicle not exceeding one-third or half its length. Body rounded

posteriorly, pointed anteriorly, not rostrate, and bearing two flexible attenuate vibratile flagella. Length of lorica ob mm., diameter To mm.; body occupying about one-half of its internal cavity.

Hab. Fresh water, attached to Conferva. Stoke Newington, London, W. S. K.

Bicosæca inclinata, n. sp., Pl. CV., Fig. 18. Lorica ovate, set obliquely on a slender pedicle of twice its length. Body occupying two-thirds of the cavity of the lorica, flagellum single. Length of lorica ob mm., greatest diameter Ito mm.

Hab. Fresh water, attached to Conferva. Stoke Newington, London, W. S. K.

ANTHOPHYSA, Duj. (revised). Animalcules pyriform, obliquely truncate anteriorly and furnished with two flagelliform appendages, attached singly or in clusters to a simple or branching uncontractile stem. Increasing by longitudinal fission.

Anthophysa solitaria, Bory, Pl. CV., Figs. 19, 20. Animalcules grouped in a cluster of forty or fifty at the extremity of a simple flexible thread-like stalk. Length of bodies go mm.

Hab. Fresh water, on Conferva, &c. European Continent, Bory and Tresenius. Stoke Newington, London, W. S. K.

Anthophysa laxa, n. sp., Pl. CV., Fig. 21. Animalcules disposed singly, excepting during fission, at the extremities of a loosely and irregularly branching flexible stalk. Length of bodies šo mm.

Hab. Fresh water, on Conferva. Stoke Newington, London, W. S. K.

Anthophysa Bennettii, n. sp. Animalcules stationed singly or in pairs (during fission) at the extremities of a slender, rigid, and repeatedly dichotomously dividing stalk. Length of bodies atomm., of the branching stalk 1 mm. and upwards.

Hab. Fresh_water, attached to Conferva. Stoke Newington, London, W. S. K.

Monas termo, Ehr. Having encountered the attached form referred to this species by Prof. James Clark, I differ from him in his assumption that the animalcule possesses a distinct mouth, having on many occasions observed it to take in food on the lateral as well as the anterior surface of its body, it investing and engulphing its prey with an expansion of its protoplasm after the manner of Amoeba. On numerous occasions I have also certified the presence of two instead of only a single flagelliform appendage.

ADDENDA. In Anthophysa the interception of food is similar to that of Monas. In Codosiga and Salpingeca it takes place anywhere within the area circumscribed by the membranous collar, the discharge of focal matter being effected within the same limits.

II.-Note accompanying Three Photographs of Degeeria domes

tica, as seen with Mr. Wenham's Black-ground Illumination and a Power of 1000 diameters. By Dr. J. J. WOODWARD,

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(Read before the Royal MicROSCOPICAL Society, Nov. 1, 1871.) MR. WENHAM having very kindly sent me one of the small truncated lenses designed by him to obtain, under certain conditions, black-ground illumination with high powers, I carefully tried it on the Degeeria domestica in the manner described in his paper in the July number of the Monthly Microscopical Journal,* using the immersion fath of Powell and Lealand as the objective. I had no difficulty whatever in obtaining the appearances of the scale described by Mr. Wenham and also several other aspects, and must regard the contrivance as a valuable addition to our means of studying semi-transparent objects with high powers.

The illumination of the scale by this method, when a coal-oil lamp was the source of light, was so brilliant that I thought probably it would be possible to photograph some of the more striking appearances. I obtained on the first trial three negatives, of which I send prints. The same scale is shown in each magnified 1000 diameters. The objective (the immersion fath) remained at the same cover correction, the position of the truncated lens and parabola was unaltered, and the different appearances exhibited resulted from trifling alterations in the position of the plane mirror by which the parallel solar pencil was thrown upon the parabola, and slight modifications of the fine adjustment. Of the prints sent, No. 2 agrees pretty well with Mr. Wenham's description. The same can hardly be said of No. 3, however, and Nos. 1 and 3 are only examples of some of the manifold results attainable by this method with which, indeed, almost as many appearances can be seen as with transmitted light.

The time of exposure required for these negatives was but three minutes. I infer from this and many other circumstances, that the semi-transparent scales are simply made luminous by the light passing into them from below, whence it results that the surface appearances are necessarily complicated by the optical properties of the structures beneath.

I understand this to be substantially Mr. Wenham's view also, and am therefore at some loss to comprehend the sense in which he speaks of the scales as being shown "opaquely” by this method.t * P. 7.

† P. 7, and note loc. cit.

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