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Show 1882.] MR. S. O. RIDLEY ON THE CORALLIID^E. 227 be due to the same causes as those which produce certain perforations, open at both ends, in the base of some of the small branches, and which are seen in parts forming passages covered in by a thin lamina of hard matter. The latter resemble so much the passages which are seen among the branches of many Stylasterida, and which are said (see Moseley, Report on Corals of the ' Challenger' Expedition, p. 78) in this case to be produced by the growth of the coral over an intruding Aphroditacean Worm which has adhered to the branches, that I must attribute with probability a similar origin to those of the Corallium. It is a different matter with the deeper tubes belonging to the main stem and branches. In the present base of the main stem, they are seen by its fracture to be excentric in position, somewhat variable in size: one of them contains a fine yellowish deposit containing minute siliceous particles and siliceous spicules, viz. spined acuates and acerates, about *14 m m . long and *009 to '0177 thick, and acerates about *28 by *024 mm., with fragments of spinulates, triradiates, and some minute anchorate spicules. Lacaze-Duthiers (Hist. Nat. du Corail, Paris, 1864, p. 333) mentions small Annelids allied to the Serpula? as sometimes attaching themselves to the surface of the Red Coral, and being covered up by the centrifugal growth of the corallum; but these tubes present no such distinct lining of carbonate of lime as this hypothesis demands. If not merely remains of the ccenosarcal canal-system, they are probably produced by the burrowing of boring Sponges (e. g. Cliona, Samus, Alectona), such as are common in Stylaster and Astraeid Madrepores, or Worms (e. g. Sipunculus), such as occur in Heteropsammia. Lacaze-Duthiers attributes such cavities generally to " la e'rosion des eponges ou des vers," and mentions that such perforated specimens of coral are technically described as " pique" by dealers. Some of the spicules mentioned above as occurring in one of the tubes appear to have been simply introduced with some bottom-material which has been accidentally washed into the tube, as their forms do not belong to any of the boring Sponges; but the spined forms mentioned may very well belong to a boring species allied to Cliona purpurea, Hancock, or Alectona millari, Carter, two species of boring Sponges. Kdlliker (Icon. Histiol. p. 146, pl. xvi. fig. 8) mentions and figures a smaller central cavity as occurring in some of his transverse sections of the Red Coral, but is unable to explain its occurrence. The question of the origin of the present passages receives, however, no help from Kolliker's observations, as his figure shows a discoloured ring surrounding the passages ; they probably represent the horny axial tract found in the stems of most coralligenous Alcyona-rians. In this case, if they prove to be constant in their occurrence, they would seriously interfere with the value of the coral for jewellery-purposes, should it be attempted in the future to put it, like the pale varieties of the Red Coral, to such a use. But the absence of a subtle tint of any kind, such as that which the varieties of the Red Coral generally possess, renders such an attempt improbable. The 15* |