230 THE OCEAN. WORLD. 
Let us pause an instant over the soft and-fleshy bark in which 
the polyps are immersed. Let us see also what are the mutual 
relations which exist between the several inhabitants of one of these 
colonies, how they are attached to one another, and what is their 
connection with the polypidom. 
' The thick fleshy body, soft and easily impressed with the finger, 
is the living part which produces the coral ; it extends itself so as 
exactly to cover the whole polypidom. If it perishes at any one 
point, that part of the axis which corresponds with the point no 
longer shows any increase. An intimate relation, therefore,. exists 
between the bark and the polypidom. If the bark is examined more 
closely, three principal elements are recognised—a common general 
tissue, some spicula, and certain vessels. The general tissue ‘is 
transparent, glossy, cellular, and contractile. 
The spicules are very small calcareous bodies, more ‘or less . 
elongated, covered with knotted protuberances 
bristling with spines, and of a more or less 
regular determinate form (Fig. 87). They refract 
the light very vividly, and their colour is that of 
the coral, but much less vivid, in consequence 
: of their want of thickness.. They are uniformly 
Fig. 87.—Coral Spicules “listributed throughout the bark, and give to the 
(Lacaze-Duthiers). coral the fine colour which generally characterises 
it when in a living state. 
The vessels constitute a network, which extends and repeats 
itself in the thickest of the bark. These vessels are of two kinds 
(Fig. 88); the one, comparatively very large, is imbedded in the 
axis, and disposed in parallel layers; the others are regular and much 
smaller. They form a network of unequal meshes, which occupies 
the whole thickness of the external crust. This network has direct 
and important’ connection withthe polyps on the one hand, and with 
the central substance which forms the axis on the other. It com- 
municates directly with-the general cavity of the body of the animal, 
by every channel which approaches it, while the two ranges of net- 
work approach each other by a greater number of anastomosing 
processes. Such is the vascular arrangement of the coral. 
The circulation of alimentary fluids in the coral is accomplished 
by means of vessels near to the axis, without, however, directly 
anastomosing with the cavities containing the polyps which live in 
the polypidom ; they only communicate with these cavities by very 
delicate intermediary canals. The alimentary fluids they receive 
+> fram the secondary. system of network, which brings them into direct, 
