CORALS. 
5°5 
A SIMPLE CORAL, TllCCOCyathuS 
(uat. size). 
to consider those corals which do not typically form stocks, but remain at the stage 
of a simple sea-anemone, only with a rigid, calcareous skeleton supporting, and no 
doubt protecting, them in different ways. All the corals found in British seas are 
(with the exception of the so-called tuft-coral) single, and generally very small. As an 
example of a regular, circular, solitary coral, we may take Thecocyathus cylindraceus, 
the skeleton of which is shown in the illustration. The 
animal when expanded fills up the central depression, but 
when, on expelling the greater part of the watery contents 
of its cavity, it contracts, the whole body seems to sink 
into the hollow cup formed by its skeleton. In the 
illustration we see only the outer wall and the top of the 
ring of septa, which are solid vertical plates, rising up 
from the pedestal secreted by the foot and radiating out¬ 
wards in all directions. Two other solitary corals are 
worth describing, as they show certain interesting special¬ 
isations. Both of them may increase by budding, that is, 
by the method which, in colony-forming corals, leads to the 
formation of stocks, if the buds remain attached to their parents. When, however, 
solitary corals bud, the buds fall off, and lead solitary lives like their parents. 
Most of the numerous species of the scarlet crisp-corals ( Flabellum ) are 
individuals, and are characterised by the slit-like form of the mouth. At a in the 
illustration the living animal is seen from above, while b shows a side view of the 
skeleton, which is attached. It resembles a pair of fans fastened along their edges ; 
and just inside the outer edges of the fans is the row of tentacles. The whole 
animal is as if the upper end of a circular polyp had been squeezed, so that the 
moutli-area, instead of being round formed a long oval (a). An interesting case of 
budding occurs in these corals, 
the buds falling off. In the 
illustration, c shows the bud 
growing out at the top of an 
individual like 6. In this 
budding condition the coral 
might pass for a different species 
of Flabellum. The bud, how¬ 
ever, ultimately falls off (d), but 
instead of becoming attached, 
is swept by the waves into some 
rocky fissure, where it spends the 
rest of its life. Besides the fact 
that it remains unattached, this bud differs from its attached parent in a far more 
important respect. It can produce eggs, which the fixed coral can not do, so that 
we have here another case of alternation of generations. Out of the egg comes 
an attached form, which buds and produces the free unattached form, which again 
produces eggs, and so on. The predominating colour of this species is a beautifully 
intense and yet transparent red, the mouth-disc having almost always broad bands 
of darker red, most marked in the paler specimens. 
scarlet crisp-coral, Flabellum (nat. size.) 
