. Cassell's natural history. Animals; Animal behavior. 272 iTuuAi. Hivrom protrusion takes place at the upper part of the cell, which generally remains soft and flexible, and can often be drawn in, forming a sheath for the tentacles when the alimentary portion of the animal IS letracted withm the lowei and haidei portions of the ti'ue cell, and can be again everted on their re-appearance. The so-called orifice- of the cell (Fig. 20, or) is in some instances protected by a row of spinesâa tac- tile horny sheath crowned with bristlesâand is in others eflectually closed by a movable lip or shutte
. Cassell's natural history. Animals; Animal behavior. 272 iTuuAi. Hivrom protrusion takes place at the upper part of the cell, which generally remains soft and flexible, and can often be drawn in, forming a sheath for the tentacles when the alimentary portion of the animal IS letracted withm the lowei and haidei portions of the ti'ue cell, and can be again everted on their re-appearance. The so-called orifice- of the cell (Fig. 20, or) is in some instances protected by a row of spinesâa tac- tile horny sheath crowned with bristlesâand is in others eflectually closed by a movable lip or shutter controlled by muscles specially developed for the purpose (Fig. 'H, a). The shape of the animal cell is exceedingly variable. Sometimes the exterior is quite plain, or it may be rugged, spinose, or elegantly sculptured, as in the sea- scurfs. In others it is punc- tured with minute pores, which permit of the entrance of the sea-water. The larger of these are occasionally pro- tected by delicate teeth like sieve, and guards against the introduction i. rig. 19.âA, ALOYONIDIUM GELATINOSUM. (After Van Benedcn.] OF HELGIUM. n, PLVMATELLA ALLMANI. BROMLEY LOUGH, (Enlavoed, after Hancock.) processes, or a fine calcareous network, which acts into the interior of the cell of foreign substances, which might prove injurious or inconvenient to the occupant thereof. (Hincks.) Portions of the intervening outer cell-walls are occasionally of thinner structure, and contain minute perforations, through which the soft contents of the various cells are conveyed. These " communication plates" permit of that slow interchange of vital fluid which, with the exception of the association in a common lodgment, is the sole connection now believed to exist between the diSerent members of the same colony. Within this double-walled sac, or animal cell, the alimentary organs of the Moss-animal are suspended in the perivisceral cavity (Fig. 20, d), and float freely in a colourless fluid, consis
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