NATURAL HISTORY. 
131 
ROOM III.] 
naturalist. The specimens usually shewn in collections are small indivi¬ 
duals which grow in the sheltered places among the rocks, where they 
are not exposed to the action of the waves, and collected before they 
have reached their proper magnitude. The form of the masses appears 
to be greatly influenced by the positions in which they have grown, 
and the size of the individuals greatly depends on the quantity of 
nourishment they are able to procure. This is proved by the fact, that 
if all the individuals of the same mass are equally exposed, they are of 
an equal size, but if the surface of the coral is w 7 aved, as in the Ex- 
planaria , (Case 13,) the individuals on the convex part of the mass, 
w’hich could procure the most food, are large, w 7 hile those in the concave 
or sunken parts are small. 
The Zoophytaria, or second order of the Zoophytes, (Cases 21 — 
28,) are easily known from the other kinds by having only six or eight 
tentacles, furnished with one or more series of short processes on each 
side. Their stomach ends in six or eight elongated processes, which 
are considered as the oviducts. One genus of these animals ( Cor - 
nularia, Case 21) is said to have a horny external skin like the 
Tubularia, into which the animal is retracted for protection. There 
are some other genera which are said to have a hard cartilaginous ex¬ 
ternal skin like the Zoanthi, as the Telesto . One genus has a similar 
tough skin, which is at length so hardened by the deposition of cal¬ 
careous matter within its substance as to become a hard coral. This 
genus of animals live in groups side by side, and as they increase in 
size form shelly tubes, which has caused them to be called Organ Coral 
or Tubipora (Case 21). At certain intervals the animals contract 
themselves into their tubes, and bend out the soft part of the outer skin 
of the body near the head, so that it forms a broad collar round the end 
of the harder tube ; and as the different animals of the same group of 
tubes generally perform this action simultaneously, the collars of the 
different tubes come in contact, and, having chalky matter deposited in 
them, unite and at length become stony like the rest of the tube. After 
this has been done, the animal begins to form another tube ; and after 
a time they repeat the same process again, so that the different tubes of 
the same group are united by cross layers into a single mass. The 
animal being bright green, and the coral vivid red, makes it a most 
beautiful object when alive. 
By far the greater number of the animals of this order have a very 
thick, spongy outer skin, which is often strengthened by having variously 
shaped calcareous grains, or rugose and more or less fusiform cal¬ 
careous spiculae, imbedded in its surface. These animals live in societies 
closely united in a single mass by their outer skin, while there appears 
to be also a general community of function in their more important in¬ 
ternal organs. They are constantly emitting buds from different parts 
of their surface, and as each species emits them in a peculiar form, the 
mass assumes a definite shape, varying in the different kinds. 
In general, the common mass has an expanded base by which it is 
attached to some marine body, and when the mass is of a low rounded 
shape, as in Lobularia , (Case 28,) the spiculae in the substance of the 
skin are strong enough to support the mass, but when the mass assumes 
an erect or a branched tree-like form, the animals secrete in the centre 
of their body a more or less rigid support, which has been called their 
