Lectures on the comparative anatomy and physiology of the invertebrate animals : delivered at the Royal College of Surgeons . ts of an outer thinand dense mem-brane, of an innerthicker membranebeset with long cilia,and of an air-bladder,which at one point, a, is attached to the above membranes, wherethere is a small constricted aperture, at least in the outer membrane is developed into a kind of crest along its upper is provided with many fine muscular fibres, and the whole bagcontracts into a small irregular mass when punctured and the airevacuated ; but it seems that th
Lectures on the comparative anatomy and physiology of the invertebrate animals : delivered at the Royal College of Surgeons . ts of an outer thinand dense mem-brane, of an innerthicker membranebeset with long cilia,and of an air-bladder,which at one point, a, is attached to the above membranes, wherethere is a small constricted aperture, at least in the outer membrane is developed into a kind of crest along its upper is provided with many fine muscular fibres, and the whole bagcontracts into a small irregular mass when punctured and the airevacuated ; but it seems that the Physalia has no power of voluntarilyemptying its air-bag. The appendages are of three kinds, — urticating, digestive, and(probably) generative. The urticating tentacles are the longest;they are hollow, and are provided with muscular fibres, of which themost conspicuous are longitudinal, and serve to retract them; theycontain many corpuscles of a reniform shape, and are richly providedwith thread-cells, whose filaments are of the spiral kind. The gastricappendages are shorter and wider, and are provided with stomata,. Physali * CXLYIII. p. 348. ACALEPH^. 177 which are applied to the prey seized and benumbed by the tentaclesIf the prey be small, it is sucked bodily into the gastric sac ; if largethe sac becomes distended with its juices and dissolved parts, thegastric secretion being a very rapid and powerful solvent. Themouth of each sac is wide, with a broad everted lip, armed with aseries of nettle-cells. The whole gastrio appendage is highlycontractile and in constant motion in the living animal. Tlie ap-pendages of the third class are cyathiform ; the development of gene-rative parts has not yet been followed out in these. The question ofthe genetic cycle of the Physalia is one of the most interesting thatremains open to the observations of the naturalist who may traversethe tropical seas where they most abound. The Physophora differs from the Physalia in having, besides
Size: 1377px × 1814px
Photo credit: © The Reading Room / Alamy / Afripics
License: Licensed
Model Released: No
Keywords: ., bookauthorowenrichard18041892, bookcentury1800, bookdecade1850
