1882. | MR. §. O. RIDLEY ON THE CORALLIIDA. 227 
be due to the same causes as those which produce certain 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 Stylasteride, 
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 
coutaining 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 Serpule 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 Astreid Madre- 
pores, or Worms (e. g. Sipunculus), such as occur in Heteropsammia. 
Lacaze-Duthiers attributes such cavities generally to “la érosion des 
éponges ou des vers,” and mentions that such perforated specimens 
of coral are technically described as “‘ piqué”’ 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. 
Koélliker (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 dis- 
coloured ring surrounding the passages ; they probably represent the 
horny axial tract found in the stems of most coralligenous Aleyona- 
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 tuprobabls. The 
15 
