oclxsx Polyps. RADIATA. Actinoids. 
Glass— POL Y V\— {Polyps). 
All idea of tlie Pohjpt is readily obtained froni the 
Sea anemone ; all are much like that, either 
small, in colonies, or large, in single groups. 'I'here is 
an analogy between the Polyp and the Garden Aster, 
though the resemblance is not homological. The 
Sea-anemoiie may be said to imitate the Aster, in 
having a row of petal-like organs around a centre, its 
mouth; and in some cases the coloring is so fine that 
the (lifFerence between the two can be observed with 
difficulty. 'I'he similarity is less observable in the 
body, however, which in the Polyp is large and fleshy. 
A species of Gampanularia found on our shores has 
more the real flower-like aspect than any other; its 
petals are highly colored and diversified in form, and 
the stem is slender, proportionately, like that of the 
garden plant. 
HALGYONOIDS. 
This is the highest group of the lowest class of 
Radiates, and is represented in the waters of the 
Northern States by one genus, 'i'he tentacles of 
these forms are limited to eight; many of them are 
quite complicated, being divided and lobed, and pre- 
senting a curiously fringed aspect resembling moss. 
They live in deep water, attached to the dead shells. 
Though seldom seen on shore, they are frequently 
brought up on the lines by fishermen, to whom they 
are known by the name of “Dead-men’s Fingers.” 
When the polyps are extended, the creature is pleas- 
ing and graceful, but very unsightly in the contracted 
slimy condition in which the sea-faring people find it. 
It is a mass of cartilaginous matter, holding some 
portion of lime in its substance. 'I’he polyps are 
increased entirely by budding. 
MADRPJPORIANS. 
One species only of this order is found in the cold 
waters of the North. 'I’he Astrangia (A. danm) is 
a proper Coral form, regarded with much interest, and 
was quite unknown until recently, when specimens 
were found on the shores of Long Island and in Vine- 
yard Sound. On the surfaces of angular broken 
fragments of rock, this little Coral may be found. It 
is a very flat and delicate form, and somewhat re- 
sembles the small Astreas of warmer waters. It 
buds from the base and spreads out, but does not in- 
crease in thickness, ft is not a Reef-building Coral 
like those of Florida and other warm regions ; the 
diameter seldom exceeding two to three inches. 'I’he 
tentacles show j)lainly the warty depositaries of the 
powerful stinging apparatus common to all of this 
class. 
A CTIN OIDS — {Sea-anemones). 
'I’his order includes the large number of interesting 
forms which, when fully expanded, so much resemble 
flowers of the garden, that they have been called 
Ocean-flowers. When closed or contracted they pre- 
sent a most uninviting appearance, which is usually 
the case when an acquaintance is sought. Like crea- 
tures of a higher sensibility, however, they are sus- 
ceptible to kindly treatment, and gradually become 
familiar, unfolding theii’ beauties fearlessly in the 
aquarium. 'I’he Actinia (Metridium marginatum) 
is the most common species of the order on our 
coast, and is very abundant in some localities, though 
its haunts are often overlooked. 'I’he obscure crev- 
ices ill the broken rocks situated between tides, are 
the favorite places. 
On the Florida Reef there are forms of this order 
which have lime cells, and are Corals. 'I’he Brain 
Corals (Meandrinas) exhibit a number of beautiful 
shapes, ranging from pretty hemispheres to indefi- 
nite masses ; these form an important element, with 
the Astreas, in the great work of Reef-building. 'I’he 
islands (called Iceys, or cays, from the Spanish cayo, 
an islet) are made up entirely from the work of the 
Polyps and allied forms. 'I’he whole peninsula of 
Florida, according to Agassiz, is so formed. 'I’he 
fact has been demonstrated that the curious hum- 
mocks which are found in all parts of the State are 
known to be old Coral Reef; this is seen in regular 
rows, interrupted uniformly by an intervening wet 
place, called an everglade. 
'I’he process of Reef-building is an interesting one. 
We will suppose that the sea-bottom is first visited 
by a single egg from the Astrea, a small delicate 
speck of jelly. In a few days this has begun to show 
a few tentacles, and is apparently, if we should ex- 
amine it, nothing more than a Sea-anemone ; but, in a 
few weeks, while the little Polyp has been establish- 
ing itself, it has also been secreting a little lime at 
the bottom of its tube, and fastened itself thereby to 
the object that it may have fallen on — perhaps a 
Clam-shell. Now there will soon be seen a growth 
of lime upon the edges and sides of W\& Polyp-, it 
loses its likeness to a Sea-anemone, and is covered 
by a white, jagged coating of lime. Soon another 
one is growing out alongside of the first, and the ani- 
mal is also capable of sending forth eggs as well. 
'I’he single Astrea has now become two, by the pro- 
cess of growth much like that of the branching of 
vegetables, and this goes on indefinitely. Wliile 
some species seem, after a time, to attain a definite 
form, and there remain, the Astreas are indefinite in 
form, and are thus a valuable element in this great 
work of building a continent. Besides the actual 
bulk which the stony Astreas add to the work, there 
are many other forms which are brought in incident- 
ally, and somewlmt dependent on the first. When 
the bottom has become covered by the Coral rock, 
there are numerous causes to [irodnce a decay of the 
Polyps. When these are dead, the pores of the Coi'al 
are filled up by siind, which adds a little to the heigh!,; 
other Corals grow upon this, and the natural debris, 
which is always swaying about by the tide, is depos- 
ited here as well as elsewhere; then there are branch- 
ing Corals, which take root here, and Gorgonias or 
Sea-fans and feathers. All these are eaten and crush- 
ed down by a variety of great Worms and Fishes. 
The debris from these causes adds another important 
element. The great Worms (Aphroditaceans) take 
in and digest the s'ofter parts, a,nd that portion of 
