63 
Fig. 0. Actinia mesembryanthemum, the Beadlet, 
is by far the commonest of the sea-anemones on our 
coasts. It varies much in colour, but may always 
be known by the row of blue beads at the base of 
the tentacles, from which it derives its name. 
_ Suborder II. 
The Madrepores possess a calcareous skeleton, 
which exactly reproduces the form of the animal, 
even in the species which live singly, for it is not 
only the outer wall which is solid, but as many 
vertical calcareous partitions project from the cup 
towards the middle, as there exist mesenterial folds 
and tentacles, 
Most madrepores form colonies, and they are 
very numerous in the tropical seas, where they form 
reefs and barriers at a moderate depth, which re- 
semble the most beautiful submarine gardens. 
In the Pacific Ocean, the coral reefs are most 
dangerous to ships; and they likewise form the 
foundation of innumerable islands, where the Cocoa- 
nut and bread-fruit tree establish themselves long 
before they are followed by man, Three kinds of 
coral-formations are distinguished. The frzngzng reefs 
skirt the edge of the land. There is often a more 
or less broad channel between the land and the reef; 
and this formation is called a darrier-reef. The reef 
lies opposite the shore, and forms a strong barrier 
against the waves; and the water in the lagoon 
generally offers a safe anchorage. These barrier- 
Madreporaria. 

reefs are often of great extent; and that which 
fringes the coast of North Australia extends for a 
distance of 1250 miles. The third class of coral 
formation is the Coral Island, or Atoll. These are 
more or less broad coral-reefs which surround a sheet 
of water. There are channels through the reef, and 
in the middle of the ring there is often a mountain 
rising from the bottom of the sea. As soon as the 
summit of the reef reaches the surface, it collects a 
layer of soil on which seeds take root. These Atolls 
are generally found in clusters. Of course they must 
be founded where reef-corals rise from the bed of the 
sea to within a short distance of the surface. This 
process has been going on for ages, and many lands 
owe their foundation to the labours of the coral 
animals, often popularly, but incorrectly termed coral- 
insects, 
The skeletons of three reef-corals are figured 
on Plate XXX. 
Fig. p. Madrepora verrucosa forms a tree-like 
colony. 
Fig. q. Fungia scutaria illustrates the mush- 
room corals, which form no colonies of large extent 
(the figure represents a single individual. The calyx 
is longitudinally contracted, and there is a cleft leading 
to the body-cavity of the animal. 
Fig. r. Echinopora gemmacea is one of the 
stony corals. Each star forms the dwelling of a 
separate animal, and by the complete petrifaction 
of the central foundations, arises a massive colony 
in which the separate calyces are embedded, 
Class IV. Porifera. 
The Sponges difier from the higher Ca@/enterata | do not form colonies are cylindrical hollow animals 
in the want of urti- 
cating organs, and 
the whole Class 
stands at a very low | 
level. No Sponge ~ 
possesses the power 
of voluntary motion, 
and most of them 
form colonies in 
which the individuals 
are all connected by 
channels. Deposits 
ofhorny, calcareous, 
or siliceous matter * 
form a firm ground- 
work, overlaid by 
the animal substance. 
Many species are 
met with, encrusting 
stones and shells on 
the bed of the sea, 
or are found in 
clusters adhering to 
rocks, like the 
sponges used for 
washing purposes, 
Others again form 
tree-like colonies; 
but, there= is) no 
spontaneous motion 
of tentacles to reveal 
their animal nature 
to the naked eye. 
The sponges which 

with no subdivision 
of the body-cavity. 
Thesea water which 
enters through nu- 
merous microscopic 
openings intheframe- 
work of the animal, 
always contains 
microscopic —orga- 
nisms which serve 
for food. A large 
opening at the ex- 
tremity of the longi- 
tudinal axis of the 
sponge serves to 
discharge the super- 
fluons water; and 
the movement of 
the water in the 
required direction is 
due to cilia, with 
which the cells of the 
body of the sponge 
are covered. The 
openings by which 
the separate animals 
discharge water look 
like large craters on 
the colony of the 
sponge. 
Sponges may 
be divided according 
to the structure of 
the skeleton, without 

