| OCR Text |
Show 18/4.] MR. G. BUSK ON A NEW POLYZOON. 29 2. Notice of a New Polyzoon (Hippuraria egertoni). By GEORGE BUSK, F.R.S., V.P.Z.S., &c. [Eeceived November 26, 1873.] (Plate V.) The subject of the present communication is so peculiar in its conformation and in several respects so widely different from any other Polyzoon with which I a m acquainted, that it seems desirable that some notice of it should be placed on record, although I a m unable from want of materials to give a full account of its structure. This can only be made out from the examination of fresh or perfect specimens that have been preserved in spirit. The only specimen at present available is not sufficient for the purpose, owing to its having been dried and reexpanded. I am indebted for it to Sir Philip Egerton, who discovered the species growing upon the carapace of a Gonoplax angulatus dredged up at Berehaven in the course of last summer. It will, no doubt, when once made known, be found in sufficient abundance ; and the examination of it, in the living or recent state, will well reward the observer. The specimen, which is preserved in the British Museum, consists apparently of only a portion of a larger growth. It is about a | of an inch in length, and consists of a central tubular stem upon which are four nodular enlargements at nearly equal distances apart. From each of these nodes spring on all sides numerous slender transparent tubes, about 0""13 long, each of which supports at the extremity a pyriform zoocecium about 0 "-04 in length. The central stem is a hollow, thick-walled, chitinous tube, obscurely jointed between the nodosities (Plate V. fig. 2 ) . The latter, in the present condition of the specimen, are quite opaque; and consequently it is impossible to make out their exact relations to the tubular stem, or the precise mode of origin of the celliferous tubules which spring from them. The tubules or peduncles, as they may be called, of the zoocecia are slender and very transparent, about -^^ of an inch in diameter, and smooth on the exterior. Internally they exhibit what appears to be an irregularly spiral filament ; but the real nature of this structure has yet to be ascertaind. The zoocecia are seated at the extremities of the tubules, to which they appear to be connected by a joint. I have been unable to make out whether there is any communication between the tube and the cavity of the zoocecium. The zoocecia or cells are of an elegant pyriform shape, somewhat gibbous on one side, which may be termed the dorsal, whilst on the opposite or anterior the zoocecium at first sight appears to be furnished with a wide aperture closed with a thin membrane similar to that which is met with in very many of the Cheilostomata (as Bicellaria & c ) , in which area is placed the true mouth with its movable lip. Nothing of the kind, however, appears to exist in Hippuraria ; and the apparent aperture represents the outline of a distinct smaller compartment of the zoocecium, placed as it were on |
