. The microscope and its revelations. may take place either from the bodies of the polypides themselves, whichis what always happens when the cells are in mutual apposition,or from the connecting stem or stolon, where the cells are distinctone from the other, as in Laguncula. In the latter cast- there isfirst seen a bud-like protuberance of the horny external integu-ment, into which the soft membranous lining prolongs itself ; thecavity thus formed, however, is not to become (as in Hydra and itsallies) the stomach of the new /.iioid, but it constitutes the chambersurrounding the digestive visc
. The microscope and its revelations. may take place either from the bodies of the polypides themselves, whichis what always happens when the cells are in mutual apposition,or from the connecting stem or stolon, where the cells are distinctone from the other, as in Laguncula. In the latter cast- there isfirst seen a bud-like protuberance of the horny external integu-ment, into which the soft membranous lining prolongs itself ; thecavity thus formed, however, is not to become (as in Hydra and itsallies) the stomach of the new /.iioid, but it constitutes the chambersurrounding the digestive viscera, which organs have their originin a. thickening of the lining membrane that projects from one sideof the cavity into its interior, and gradually shape> itself into thealimentary canal with its tentacular appendages. Of the produc-lion of gemma- from the polypides themselves the best examples arefurnished by the Flnstro and their allies. From a single cell of tin-Klustrse five such buds may he sent oil, which develop themselves. POLYZOA 907 into new polypides around it; and these in their turn produce budsfrom their unattached margins, so as rapidly to augment the numberof cells. To this extension there seems no definite limit, and it oftenhappens that the cells in the central portion of the leaf-like expan-sion of a Flustra are devoid of contents and have lost their vitality,whilst the edges are in a state of active Independently oftheir propagation by gemmation, the Polyzoa have a true sexualgeneration, the sexes, however, being usually, if not invariably, unitedin the same polypides. The sperm-cells are developed in a glandularbody, the testis, m, which lies beneath the base of the stomach, orthey are developed from large portions of the inner surface of thebody-wall; when mature they rupture, and set free the spermatozoa,q q, which swim freely in the liquid of the visceral cavity. The ova,on the other hand, are formed in an ovarium, n, which is lodged inthe m
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Keywords: ., bookcentury1900, bookdecade1900, booksubjectmicrosc, bookyear1901
