In the _Red Coral_, so largely employed in the manufacture of beads, brooches, and other ornaments, not only the animalcules, but also their receptacles, are composed of a soft perishable substance. When alive, the polypes, as well as the investing fleshy integument, are of a delicate bluish tint; the internal calcareous axis alone possesses the peculiar red colour. Upon being taken out of the sea, vitality quickly ceases, the soft parts decompose, and the beautiful crimson stone commonly known as the _true coral_, is obtained free from all traces of the soft mass by which it was secreted. Although an actual investigation of the facts described can only be instituted near the seas of warm climates, yet our coasts abound in certain coral-zoophytes in which similar phenomena may readily be observed. Most persons in their rambles by the sea-side must have noticed on the fuci, algæ, shells, pebbles, &c., patches of a white earthy substance, which when closely examined resemble delicate lace-work. These apparently calcareous incrustations are clusters of the zoophytes termed the _Flustra_, or sea-mat.[AT] When removed from the water, this aggregation of polypes seems coated over with a glossy film or varnish; and with a lens of moderate power the surface is seen to be full of pores, disposed with much regularity. If viewed under the microscope while immersed in sea-water, a very different appearance is presented. Every pore is found to be the opening of a cell whence issues a tube fringed with several long feelers or arms; these expand, then suddenly contract and withdraw into the cell, and again issue forth; the whole surface of the Flustra being covered with these hydra-like animalcules. The Flustra, therefore, like the corals, constitutes an assemblage of polypes, each individual being permanently fixed in a durable cell, and the whole attached to a common integument by which the calcareous frame-work was secreted and maintained.[AU] [AT] See '_Wonders of Geology_,' Plate 5. [AU] See Dr. Johnson's beautiful work on '_British Zoophytes_,' in which are numerous figures of various species of Flustra. Note X. Page 53. _Infusorial earth from Richmond in Virginia._ [Sidenote: INFUSORIAL EARTHS.]