CORALS. 
5i7 
We conclude our description of these 
corals ( Tubiporidce ), a family consisting of 
of which are neither numerous nor varied. 
The individuals resemble in form, in the 
number of their delicate tentacles and in 
their soft anterior body, the other living 
members of the order. In the structure of 
their skeleton they are, however, unique 
among extant corals, and recall certain 
extinct forms. Each individual secretes 
a smooth-walled tube, without calcification 
of the vertical septa. These tubes, which, 
like the pipes of an organ, stand almost 
parallel, are united to form a stock by 
means of transverse platforms. These 
latter do not, however, correspond with 
eight-rayed corals with the organ-pipe 
the one genus Tubipora. the members 
RED CORAL. 
A, Part of a stock with retracted polyps, two have 
been opened (magnified) ; j5, With polyps more 
or less extended ; a larva (a) seen in the act of 
emerging through the mouth of the uppermost 
polyp. 
ORGAN-riPE coral, Tubipora (nat. size). 
the inner transverse parti¬ 
tions ( tabulae ,), by means of 
which the upper living part 
of the tube is from time to time cut off from the dead part below. The 
transverse platforms are neither regularly parallel nor continuous; neverthe¬ 
less they do indicate in a general way stages of growth. They are very richly 
provided with nutritive canals, and are of special importance for the whole stock, 
inasmuch as the young individuals bud out from their surfaces. As the longer 
tubes grow, the intervals between them increase, and as soon as there is room 
enough for a new polyp, one buds out from the platform. Division of the 
individuals or formation of buds from the tubes themselves does not take place in 
this family. 
STRUCTURE OF ORGAN-PIPE CORAL. 
a, Starting points of new individuals 
(nat. size.) 
Coral-Reefs Having described a few typical corals, and explained their 
and islands, general structure and characters, some mention must be made of the 
importance of these creatures in the economy of nature. Whereas most forms of 
