5 16 
CCELENTERA TES. 
so that the whole structure looks like a spiral staircase constructed of fine cord. 
The accompanying illustration shows an allied form ( Streptocaulus ) of the family 
Chrysogorgoniidce, as yet found only in the Western 
Atlantic. The simple or branched colonies are as thin 
as horsehair, and the delicate axis has a golden sheen, 
with a beautiful display of colours. 
The genus Isis, the stock of which is partly horny 
and partly purely calcareous, forms a transition between 
the above and the red coral (Cor allium rubrum). In 
the latter the axis is calcareous, and built of numerous 
fine layers, the microscopic structure of which is so 
definite that a connoisseur can detect false from real 
coral. The fresh axis is covered with fine longitudinal 
furrows, in which run the deepest of the canals connect¬ 
ing the polyps with one another. The stocks, as a rule, 
consist either purely of male or purely of female in¬ 
dividuals, although occasionally the two sexes are found 
on one and the same stock, and even individual polyps 
which are both male and female sometimes occur. In 
the illustration, a slightly magnified branch of a stock 
is represented, with several retracted polyps and two 
cut open. In the upper exposed calyx (o), eggs are seen, 
while the lower ( t ) contains a large male vesicle, and at 
its side an egg (o). After hatching, the ciliated larvae 
leave the egg while still within the chambered cavity of 
their parent ( B ). Two of the long worm-like larvae (/, g) 
can be seen in the illustration through the delicate body- 
wall of a polyp whose tentacles are retracted, and others 
are visible in a cell which has been cut open. In the 
uppermost cell a larva (a) is seen in the act of passing 
out through the mouth (6). The red coral is found only in 
the Mediterranean and Adriatic seas : the most noted coral- 
fisheries being carried on off the Algerian and Tunisian 
coasts, at depths of forty to one hundred fathoms. The 
coral obtained in these fisheries varies greatly in value. 
The price of the broken pieces, often perforated by worms 
and sponges, is from five to twenty francs the kilogramme 
(2 lbs.); good coral fetches from forty-five to seventy francs, 
while choice thick coral, especially the rosy red kind, is 
bought at from four hundred to five hundred francs the 
kilogramme. Such pieces as are black, either superficially 
or throughout their whole thickness, are sold separately 
at from twelve to fifteen francs the kilogramme; these are 
not of a different species, but, having long been covered with mud, have changed colour 
as a result of chemical changes. The coral is made into articles of ornament both 
in Paris and Marseilles, but the chief industries are in Naples, Leghorn, and Genoa. 
■ >. it 0 5 KlSS-' 
co rescue w sea-fan, Streptocaulus 
pulcherrivius (nat. size). 
