Fig. 58. A Rock covered with young Polyps and Polypidom. (Lacaze-Duthiers.)
Darwin, who examined some of these creatures very minutely, tells us that "several genera" (Flustræ, Escharæ, Cellaria, Cresia, and others) agree in having singular movable organs attached to their cells. The organs in the greater number of cases very closely resemble the head of a vulture; but the lower mandible can be opened much wider than a real bird's beak. The head itself possesses considerable powers of movement, by means of a short neck. In one zoophyte the head itself was fixed, but the lower jaw free; in another it was replaced by a triangular hood, with a beautifully-fitted trap-door, which evidently answered to the lower mandible. In the greater number of species each cell was provided with one head, but in others each cell had two.
Fig. 59. Corpuscles from which originate the Polypidom.
Fig. 60. First form of the Polypidom. (Lacaze-Duthiers.)
"The young cells at the end of the branches of these corallines contain quite immature polypi, yet the vulture heads attached to them, though small, are in every respect perfect. When the polypus was removed by a needle from any of the cells, these organs did not appear to be in the least affected. When one of the vulture-like heads was cut off from a cell, the lower mandible retained its power of opening and closing. Perhaps the most singular part of their structure is, that when there are more than two rows of cells on a branch, the central cells were furnished with these appendages of only one-fourth the size of the outside ones. Their movements varied according to the species; but in some I never saw the least motion, while others, with the lower mandible generally wide open, oscillated backwards and forwards at the rate of about five seconds each turn; others moved rapidly and by starts. When touched with a needle, the beak generally seized the point so firmly that the whole branch might be shaken."
In the Cresia, Darwin observed that each cell was furnished with a long-toothed bristle, which had the power of moving very quickly; each bristle and each vulture-like head moving quite independently of each other; sometimes all on one side, sometimes those on one branch only moving simultaneously, sometimes one after the other. In these actions we apparently behold as perfect a transmission of will in the zoophyte, though composed of thousands of distinct polyps, as in any distinct animal. "What can be more remarkable," he adds, "than to see a plant-like body producing an egg, capable of swimming about and choosing a proper place to adhere to, where it sprouts out into branches, each crowded with innumerable distinct animals, often of complicated organization!—the branches, moreover, sometimes possessing organs capable of movement independent of the polypi."
Passing to the coral fishing, it may be said to be quite special, presenting no analogy with any other fishing in the European seas, if we except the sponge fisheries. The fishing stations which occur are found on the Italian coast and the coast of Barbary; in short, in most parts of the Mediterranean basin. In all these regions, on abrupt rocky beds, certain aquatic forests occur, composed entirely of the red coral, the most brilliant and the most celebrated of all the corals, Coralium decus liquidi! During many ages, as we have seen, the coral was supposed to be a plant. The ancient Greeks called it the daughter of the sea (Κορύλλιου κόρη ἁλός), which the Latins translated into corralium or coralium. It is now agreed among naturalists that the coral is constructed by a family of polyps living together, and composing a polypidom. It abounds in the Mediterranean and the Red Sea, where it is found at various depths, but rarely less than five fathoms, or more than a hundred and fifty. Each polypidom resembles a pretty red leafless under shrub bearing delicate little star-like radiating white flowers. The axes of this little tree are the parts common to the association, the flowrets are the polypi. These axes present a soft reticulated crust, full of little cavities, which are the cells of the polyps, and are permeated by a milky juice. Beneath the crust is the coral, properly so called, which equals marble in hardness, and is remarkable for its striped surface, its bright red colour, and the fine polish of which it is susceptible. The ancients believed that it was soft in the water, and only took its consistence when exposed to the air:—