ACTINOZOA. 99 
not divided by vertical partitions (septa), but which are con- 
nected by strong transverse plates. The coral is bright red in 
colour, and the polypes are usually bright green. 
The best known, however, of the Alcyonaria is the family 
Gorgonide, represented by the sea-shrubs, fan-corals, and the 
red coral of commerce. A few of the members of this family 
are British, but they attain their maximum in point of size and 
numbers in the seas of the tropics. In all the Gorgonide the 
organism consists of a composite structure made up of numer- 
iN 7h Ty 
iV LP 
Fig. 39.—Sclerodermic and Sclerobasic Corals. @ Portion of branch of Dexdro- 
phyllia nigrescens, a sclerodermic coral (after Dana); 4 Longitudinal section 
of Isis hippuris, a sclerobasic coral, exhibiting the external bark or ccenosarc, 
with its imbedded polypes, supported by the internal axis or skeleton (after 
Jones). 
ous polypes united by a common flesh or coenosarce (fig. 39, 2), 
the whole supported by a central branched axis or coral. The 
coral varies in composition, being sometimes calcareous—as in 
red coral—sometimes horny, and sometimes partly horny and 
partly calcareous, as in /szs (fig..39). In all cases, however, the 
corallum differs altogether from the sclerodermic corallum, 
which has been described as so characteristic of the reef-build- 
ing corals. The coral in the present instance is always what is 
called “sclerobasic ”—that is to say, it always forms an internal 
axis, covered by the coenosare with the polypes produced there- 
