OCR Text |
Show 30 MR. G. BUSK ON A NEW POLYZOON. [Jan. 6, the front of the larger or hinder one, and about half its length. external walls of both compartments are very thin and transparent, and marked with fine irregular transverse lines. The orifice through which the polypide is protruded appears to belong chiefly, if not entirely, to the smaller compartment, in which may be perceived a dark opaque body probably representing the contracted remains of the polypide, from which in several of the zoocecia the usual contractile, muscular fasciculus proceeds. The two compartments seem to be separated by an obliquely vertical septum, in which may be obscurely perceived a circular opening*, through which the retractile muscle appears to pass to the bottom of the hinder compartment. Besides these structures there may be seen traces of other, probably muscular, bands in the larger compartments ; but the whole of the internal economy has yet to be satisfactorily made out. In most of the zoooecia the remains of the protruded polypide may still be seen projecting from the apical orifice. I have been unable to discern any fringe of setae, but have no doubt that it will be found that, when the polypide is protruded, its base is surrounded with at least a membranous fringe, as is the case in many of the Ctenostomata. Some idea of the appearance presented by the Polyzoon when alive may be formed from fig. 3 in the accompanying Plate, taken from a sketch made by Sir Philip Egerton. From this it would seem that the zoocecium, at any rate on occasion, is capable of being flexed to a right angle upon its peduncle, although in the dead specimen all the zoocecia are continued in a straight line with it. For this interesting production I propose the name of Hippuraria egertoni, with the following diagnosis:- Suborder CTENOSTOMATA. Fam. HIPPURARIAD^E, n. fam. Gen. HIPPURARIA, n. g. Stem jointed, nodular, whorls of celliferous tubules arising from the nodes. Zoocecia two-celled. Sp. HIPPURARIA EGERTONI, n. sp. The only species. Hab. Berehaven, Ireland (parasitic on Gonoplax angulatus). DESCKIBTION OF PLATE V. Fig. 1. Hippuraria egertoni, nat. size. 2. Enlarged about ten times. 3. Appearance when alive. 4. Anterior aspect of zoocecium. 5. Posterior aspect of zoocecium. 6. Portion of the central stem between two nodes. * This opening may probably represent that by which the zoocecia in the other Ctenostomata communicate with the tube from which they spring. |