1882.] MR. S. O. RIDLEY ON THE CORALHIDiE. 227 



be due to the same causes as those which produce certaia per- 

 forations, 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 Strjlasteridae, 

 and which are said (see Moseley, Report on Corals of the ' Chal- 

 lenger ' 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 mm. 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 Serpulse 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 distmct 

 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. Gliona, Samus, 

 Alectona), such as are common in Stylaster and Astraeid Madre- 

 pores, or Worms (e. g. Sipunculus), such as occur in Heteropsammia. 

 Lacaze-Duthiers attributes such cavities generally to " la erosion 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 witli 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. 



Kolliker (Icon. Histiol. p. 146, pi. 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 dis- 

 coloured 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* 



