| | of KERATOPHYTA. 65 
it dies, the Animal of the Millepora Coral Kind frequently 
incrufts its dead Branches with a. white coral Matter, fo that 
many Perfons have been deceived by not examining it care- 
fully, and have taken it for a calcarious, inftead of a ftony, 
| Incruftation. But, befides the Difference of the Materials of 3 
| which thefe Coverings are compofed, the Irregularity of the 
) Coral is eafily to be diftinguifhed, from the great Exadinefs 
of the natural Incruftation. | | 
~ Another Obfervation naturally follows this; and that is, 
we never find upon one and the fame Species of Keratophy- 
ton, two different kinds of calcarious Incruftations. _Not- 
withftanding I have feen three different Species of Kerato- 
phyta adhering to one Piece of Rock-coral; and in the 
cS Piece, Part of a dead Keratophyton incrufted with the 
~ Coral. ; 3 . 
The Particles of this cortical Cruft, which are of a pecu- 
liar Figure in each Species, are often deeply imprefled into 
the laft Rew of Tubes, which are now become woody or 
horny, from having their calcarious Parts mixed with the 
_glutinous Parts of the Animal, and are the prefent Surface 
of the inner Part. : 
No Bark, Membrane, or other outfide Covering, are ever 
found on this Genus of marine Produétions, except this cel- 
lular calcarious Coat, which fhews it to be its natural one. — 
Whoever has carefully examined the upright and crofs” 
~ Se&ions of Trees and Shrubs, or even the Stems of Sea- 
plants, -will find, that the longitudinal Veflels of the woody 
Parts are always connected together by lateral Fibres, or 
have lateral Tubes. But on the niceft Enquiry we could » 
make with the Microfcope, we could never difcover any of - | 
thefe conneéting Fibres, or Tubes, proceeding from the Pith 
ee) . to 
