Animal and vegetable physiology, considered with reference to natural theology, by Peter Mark Roget .. . r, immediately disappear, by diving into thestill depths of the ocean. By what processthey effect these changes of absorption and ofreproduction of air yet remains to be genera, as the Physsophora, have severalof these air-bladders; but in other respectsresemble the ordinary Medusae, in having nomembranous crest. The ActinicE are a tribe of Zoophytes, which,from the general resemblance of their forms tothose of Polypi, are by most naturalists in-cluded under that order. But
Animal and vegetable physiology, considered with reference to natural theology, by Peter Mark Roget .. . r, immediately disappear, by diving into thestill depths of the ocean. By what processthey effect these changes of absorption and ofreproduction of air yet remains to be genera, as the Physsophora, have severalof these air-bladders; but in other respectsresemble the ordinary Medusae, in having nomembranous crest. The ActinicE are a tribe of Zoophytes, which,from the general resemblance of their forms tothose of Polypi, are by most naturalists in-cluded under that order. But they exhibit amuch greater developement in their organiza-tion ; having very distinct muscular fibres, en-dowed with strong powers of contraction. Theirdigestive organs, also, as I shall have afterwardsoccasion more fully to notice, are constructedupon a more complicated plan than in the poly-pus. Fig. 86 exhibits an Actinia in its con- 198 THE MECHANIOAL FUNCTIONS. tracted state. When their tentacula, which sur-round the mouth, and are very numerous, arefully expanded, (as shown in Fig. 87,) these. animals present a striking analogy of form tomany of the compound flowers ; and accordinglythe particular species are named from these re-semblances, the sea-anemone, the sea-marygold,the sea-carnation, the sun-flower, daisy, iscc. Ac-tinia? are seen in great numbers on many shores,adhering by their flat surfaces to rocks, andbeing generally permanently fixed to their the weather is fine, and the sea calm, it isvery anmsing to watch the rapid expansions andretractions of their many coloured tentacula,while they are moving in search of food: to ob-serve the quickness with which they seize onwhatever prey comes within their reach, and tonotice the suddenness with which they collapseinto a round contracted mass, on receiving theslightest injury. Yet these animals are not of necessity con-fined to the particular spots where we see themfixed ; for they are capable, when distu
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