GELATINOSI. 
655 
their reach. Light affects them very powerfully, and they are fond of it. By division of the body 
they may be multiplied to an indefinite extent ; but their natural production is by buds, which shoot 
out from various parts of the parent animal, and drop off when they are matured. They are found in 
stagnant waters, usually under the floating leaves of aquatic plants ; and it is understood that they tend 
to purify the waters. Some are green, others of a grey colour, and they vary also in size. 
Corine, have a fixed stem and oval body, open at the summit, and covered with little tentacula. Their texture 
is firmer than that of Hydra ; some of them carry the ova on the under part of the body, in a manner similar to 
that of some Crustacea and Arachnidse. 
Cristatella, have over the mouth a double range of numerous tentacula, forming a sort of plume in the shape of 
a half-moon, the regular motion of which brings food to the animal. These mouths are on short necks attached 
to a gelatinous body, which moves somewhat similar to Hydra. They inhabit stagnant waters ; but to the naked 
eye, they appear only as little spots of mould. 
Vorticella, have the stem fixed, often much branched and divided, with a bell or horn-shaped termination to 
each branch, and two opposite groups of filaments, which agitate the water. They abound in stagnant fresh 
waters, and are arranged as bushes, shi’ubs, plumes, and other agreeable forms ; but they are too minute for being 
seen by the naked eye. 
Pedicellaria, are found between the spines of Echini, and by some considered as organs of these animals, but the 
probability is that they are Polypi, which seek shelter there. They consist of a slender stem, with a horn on the 
tip, furnished with tentacula like minute threads or leaves. 
THE THIRD ORDER OF THE POLYPI, 
CORALLIFERI. 
These include all those numerous species, which were for a long time regarded as marine 
plants, and in which numerous individuals are so united as to form compound animals, for the 
most part fixed like plants by a branched stem, or by simple expansions of a solid substance, 
at the base, or in the middle of the group. The individual animals, which are more or less 
analogous to Actinia and Hydra, are all connected in a common body, and have a general 
nutrition, so that whatever one eats, tends to the nourishment of the common body, and of all 
the individuals. Their instincts appear also to be common, at least in those species which 
have free motion in the water, for they swim by the joint action of the general body, and of 
all the Polypi. Polypidom (the House of the Polypi), is the name usually given to the common 
part of these compound animals ; but the name is not quite correct, inasmuch as the common 
part is sometimes internal, and sometimes external. These polypidoms are formed in layers 
by deposition, somewdiat similar to the ivory of teeth ; and they are of various degrees of 
hardness ; the hind parts being composed of salts of lime, but always united by means of 
animal matter, in the same manner as the lime in bones, crusts, and shells. The differences 
of form and situation in the polypidoms, gives rise to many divisions and subdivisions. 
THE FIRST FAMILY OF THE CORALLIFERI. 
The Tubularia. 
These inhabit tubes which have a common gelatinous stem pervading the axis, like the pith of a tree ; 
and the tubes open sometimes on the summit, and sometimes at the sides, for allowing a passage to the 
Polypi. These Polypi are individually very simple, and resemble in their organization Hydra and Cris- 
tatella. 
They form three principal genera, but each admits of subdivision. 
Tubipora, — 
Have the tubes simple, and of stony consistence, each containing a simple Polype, and arranged parallel 
like the pipes of an organ. 
T. nmsica, abundant in the Oriental Archipelago, has the tubes of a fine red, and the polypi green and like Hydra. 
Some fossil polypidoms, such as Catenipora, in which the tubes are disposed in meshes, and Favosites, where they 
I are crowded and hexagonal, resemble this genus. 
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