. La cyclopaedia d'anatomie et physiologie. Anatomie ; physiologie ; Zoologie. ACALEPH7E. Rhigostoma caruleu. creux ; et, lorsqu'il est connecté à l'appen- dages de l'appareil digestif des cavités, ou lorsqu'ils ont à leur base une vésicule, très extensile. Plusieurs genres ont suckers aux extrémités, et sur les côtés, de leur tentacula, par lesquels les proies qui passe est saisi. La tenta- cula qui sont extensile semblent être projetées par le forçage de l'eau dans leur cavité interne, par les contractions des vésicules à leur base. La mesure dans laquelle l'organe filamenteux est donc prolongé, dans

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. The cyclopædia of anatomy and physiology. Anatomy; Physiology; Zoology. ACALEPH7E. Rhigostoma caruleu. hollow; and, when connected with the appen- dages of the digestive cavities, or when they have a vesicle at their base, very extensile. Several genera have suckers at the extremities, and along the sides, of their tentacula, by means of which the passing prey is seized. The tenta- cula which are extensile seem to be projected by the forcing of water into their internal cavity, by the contractions of the vesicles at their base. The extent to which the filamentary organ is thus lengthened, in some species, is very extra- ordinary.* It seems to be shortened again by means of the contractions of circular muscles, which force back the water into the vesicle, and of longitudinal muscles which draw it in. Peron thought that some of the pulmograda were furnished with internal air-bladders; but Eschscholtz, on directing his attention to this point, satisfied himself that what Peron had taken for air-bladders were merely appendages of the gastric cavities, into which air had acci- dentally been introduced during the removal of the animals from their native element. Jn the cirrigrada, locomotion is effected Fig. 11.. ila septentrionalis. * In the tentacula of some of the physograda, also, a similar extensibility exists. The lower sur- face of physalus, for instance, which itself seldom exceeds six inches in length, is provided with ten- tacula sixteen and even eighteen feet long. partly by the movements of the tentacules which hang down from the inferior surface; but chiefly, perhaps, by the action of the wind on the raised crest, with which most of these animals are provided. Immediately around the mouth are placed numerous small tubular suckers, similar to the feet of many echinoder- mata. Exterior to these there are longer tenta- cula, for the most part in a single row, and simple; sometimes branched. Neither of these two kinds of organs is very extensile. The disc from

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