Animal and vegetable physiology, considered with reference to natural theology, by Peter Mark Roget .. . ndles of fibres which connect its head withthe base of the cell. The structure of the polypeis perfected by the addition of a closed capsule;and when it is first detected protruding from thecell, it possesses all the parts of an adult polype,and vibrates the cilia of its tentacula with asmuch regularity and velocity as at any futureperiod. Before the polype is capable of protrud-ing from the aperture of the first cell, the upperpart of the cell has already extended outwardsto form the rudim
Animal and vegetable physiology, considered with reference to natural theology, by Peter Mark Roget .. . ndles of fibres which connect its head withthe base of the cell. The structure of the polypeis perfected by the addition of a closed capsule;and when it is first detected protruding from thecell, it possesses all the parts of an adult polype,and vibrates the cilia of its tentacula with asmuch regularity and velocity as at any futureperiod. Before the polype is capable of protrud-ing from the aperture of the first cell, the upperpart of the cell has already extended outwardsto form the rudiment of a second : and so on, insuccession, till the whole structure is tentacula of polypi are exquisitely sen-sible, and are frequently seen, either singly oraltogether, bending their extremities towardsthe mouth, when any minute floating bodycomes in contact with them. When a polypeis expanded, a constant current of water isobserved to take place, directed towards themouth. These currents are never produced bythe motions of the tentacula themselves; l)ut 172 THE MECHANICAL are invariably the effects of the rapid vibrationsof the cilia placed on the ten-taciila. In the polypes of theFlustra carbasea, (Fig. 69),the tentacula have each asingle row of cilia, extendingalong both the lateral margins,from their base to their ter-mination.* Each polype hasusually twenty-two tentacula ;and there are about fifty cilia on each side of atentaculum, making 2200 cilia on each there are above 1800 cells in each squareinch of surface, and the branches of an ordinaryspecimen present about ten square inches of sur-face, we may estimate that an ordinary specimenof this zoophyte presents more than 18,000 po-lypes, .396,000 tentacula, and 39,600,000 other species certainly contain more thanten times these numbers.! The vibrations of these cilia are far too rapidto be followed by the quickest eye, even whenassisted by the most powerful microscope, andc
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