Midland Naturalist/Volume 01/Note On a Thecated Rotifer
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Note On a Thecated Rotifer from Sutton Park.
The last number of the “Midland Naturalist” contained a description of the rare Rotifer Œcistes pilula, which I first exhibited at a meeting of the Birmingham Natural History and Microscopical Society on the 11th of June last. The same pool in Sutton Park, whence I obtained that species, has since yielded a thecated Rotifer of large size and singular beauty, apparently not yet described, unless indeed it be identical with one recently shown by Mr. Oxley at a meeting of the Royal Microscopical Society, of which Mr. T. Bolton exhibited a drawing at the June meeting of the Birmingham Society. In the absence of all measurements it is difficult to decide whether these two animals represent the same species, but the diameter of the trochus in Mr. Oxley’s drawing appears greater than it is in my specimens, and the latter clearly show two tentacular processes, while his figures show only one, though this may result merely from the position in which the animal was sketched. But as both my observations and drawings were made before I had heard of that gentleman's, I beg leave to append a brief description, together with figures drawn under the microscope to an accurate scale, premising that, as I have only found two individuals, such description is necessarily imperfect, and that I hope next season to be able to renew my observations.
If the species has not yet received a name, I would suggest that, from the length of its slender foot-stalk, it may be appropriately christened, Œcistes longipes.
I also give figures of Œcistes pilula, drawn to the same scale.
Œcistes longipes—Total length of animal when fully extended, .045in.; when retracted, .026in.; diameter of trochus, .014in.; height of theca, .035in,; greatest diameter of theca, .029in. Theca semi-transparent, milky-white when viewed by dark back-ground illumination. Cilia of the circular trochus conspicuous, those of the cingulum clearly visible under a 1in. objective. Mastax occupying more than half the diameter of the neck. Tentaculur processes two, apparently without terminal setæ.
Ova carried after emission at base of foot-stalk. Foot-stalk corrugated, especially when retracted.
Œcistes pilula.—Dimensions of an average specimen:—Total length of animal when fully extended .025in.; longer diameter of trochus, .005in.; shorter diameter, .003; height of theca, .018in.; greatest diameter of theca, .007in.
Description of Figures.—Plate V.
Figs. 1 and 2.—Œcistes longipes.
Figs. 3 and 4.—Œcistes pilula.
This work was published before January 1, 1929, and is in the public domain worldwide because the author died at least 100 years ago.
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