280 



The coral, as it is usually seea, cousists of three distinct portions, 

 of very difFereiit texture and appearance — tlie axis, bark, and the 

 sponge. 



The axis is formed of a considerable quantity of transparent glass- 

 like fihres, slightly tvvisted from right to left into a spirai rope- 

 like bundle 18 to 20 inches in length and 3 or 3| lines in diameter 

 at the lower pait, where the fibres are most closely applied to each 

 other, and whence the specimen gradually expands upwards to a dia- 

 meter of double that extent. 



The part above this tapering base is iu different specimens covered 

 to a greater or less extent (and eridently in the perfect statė is en- 

 tirely) with a kind of leathery bark, vvith large truncated uipple- 

 shaped scattered tubercles, having flat crovvns with radiating grooves 

 and a centrai depression. 



The base of the transparent rope is (in one specimen) as it were 

 inserted into an irregular mass of a very loose spongy substauce, to 

 which it is very firmly attached ; and in passing through which it 

 gradually tapers to about half the size of the narrowest portion of 

 the exposed part, and finally terminates in a truncated pencilled base 

 of very fine capillary fibres. In general, the specimens are withdrawn 

 from this spongy base, and the lower part of the axis is cleaned ; but 

 I think it is evident that they all are attached to such a sponge in 

 their natnrai statė. 



The bark is formed of two distinct layers : the outer having the 

 appearance of an aggregation of grains of sand united together by a 

 small quantity of animal rnatter ; the iuner portion having imbedded 

 in its substance numerous very fine capillary fibres of preciselv 

 similar texture to those which form the axis of tlie coral, but of 

 much smaller size ; and this portion of the bark evidently extends 

 between and invests each of the fibres of the rope-like axis. 



The fibres which form the axis are perfectly transparent, colour- 

 less, and moderately flexible, resembling in appearance those of 

 spun glass or very clear bristles. They vary in thickness from half 

 a line to the diameter of a very fine hair. In the middle portion 

 they are nearly cylindrical ; vvithin 2 or 3 inches of the tip they 

 gradually taper to half their former diameter ; externally they ap- 

 pear to the naked eye smooth and polished, but as if furnished with 

 numerous internal cracks taking different directions. Under the 

 microscope there are seen many close-set superficial annular grooves, 

 which become more evident near the tips, where they assume the 

 form of raised belts most prominent belovv, and giving a somevvhat 

 irregular outline to the surface. Internally they are solid, and 

 formed of very numerous, very thiu, concentric coats, as may be 

 seen by breaking them transversely, when, instead of presenting a 

 straight fracture, the coats appear of different lengths, in consequence 

 of their yieldiug at different intervals. If this fracture is minutely 

 examined under a lens, each of its component laminae is found to 

 present numerous concentric lines, showing it to be formed of several 

 platės- But this structure is most evidently seen on applying the 

 end ot one of the brcken fibres to the flame of a spirit lamp, when 



