CORALLINES. 
133 
ar e of two kinds (Fig. 52) ; the one, comparatively very large, is 
mibedded in the axis, and disposed in parallel layers ; tire others are 
regular and much smaller. They form a net-work of unequal 
meshes, which occupies the whole thickness of the external crust. 
This net-work has direct and important connection with the polypes 
on the one hand, and with the central substance which forms the 
axi s on the other. It communicates directly with the general cavity 
° 1 re body of the animal by every channel which approaches it, while 
10 tw ° ranges of net-work approach each other by a great 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 anasto- 
mosing with the cavities containing the animalcules w T hich live in the 
Pmypier ; they only communicate with those cavities by very delicate 
111 enn ediary canals. The alimentary fluids they receive from the 
