KATUEAL HISTOEY OF THE EED COEAL. 
71 
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of the fluid which fills the general cavity of the body. Leav- 
ing the tentacles we find the month represented by a slit 
guarded by two soft lips. The direction of this slit is not as 
many writers declare_, from one tentacle to that immediately 
opposite ; but_, on the contrary^ has its axis intermediate between 
two tentacles : it occupies about one half of the diameter of 
the peristome and leads directly into a gullet which must be 
regarded as the true stomach. This is a transparent tube 
placed in the very centre of the animal^ and closed at its extre- 
mity by a sphincter muscle, which when not in action leaves 
the end of the gullet open, and thus forms an aperture of 
communication between the external medium (the water) and the 
internal cavity of the polypit e. The latter we must now glance 
at : it is a chamber or space bounded externally by the outer 
wall of the body becoming lost below in the tissue of the 
sarcosome, and chiefly of interest from the circumstance that 
it is divided above into eight small compartments. This 
division is efiected by membranous partitions which are con- 
tinuous outside with the general wall of the body and within 
with the outer surface of the gullet or stomach ; at the termina- 
tion of the latter organ they of course lose their inner con- 
nection, and then appear as membranous folds floating in the 
general cavity, and attached by one border to the wall of the 
body. Each chamber is continuous above with a tentacle, 
which, by the vfay, does not terminate in an aperture, as is 
generally imagined. The most remarkable feature in the 
anatomy of the septa is that they have attached to their upper 
part a number of thread-like coils which resemble the folds of 
the intestine and to which the reproductive vesicles are attached 
(flg. 2 r). Next we come to the consideration of the sarcosome 
(fig. 1 A), and in this we find three distinct constituents : 1st, a 
matrix or bed of granular or structureless material ; 2nd, scat- 
tered through this a number of crystalline particles ; and 3rd, 
peculiar systems of tubes. The matrix is already disposed 
of, it lodges all through its substance thousands of crystalline 
particles, having the characteristic tint of the coral and being 
of minute size ; to describe their form would be, as M. Lacaze- 
Duthiers very truly observes, exceedingly difficult ; but some 
notion of their outline may be conceived by fancying a pyramid 
with a square base, whose summit represents a kind of pedicle 
the edges of which are covered with two linear series of small 
projections, and whose base is irregular, shghtly prominent, 
and covered with spines itself. Besides these bodies which are 
scattered all through the sarcosome, there are two series of 
vessels — an external and internal. The inner vessels are tubes 
of large bore and with very distinct walls ; they run parallel 
to the axis of the polypidom, and occasionally anastomose or 
