OF INVERTEBRATE ANIMALS. 
403 
or, unlike almost all others, they are unable to move from place to place. The 
form of their tentacula will be seen in Fig. 4. Every animal body must possess 
some kind of solid basis or framework, in order to form a support for its softer 
parts, called its skeleton, and although in some animals this is of a very slight 
nature, in others we have a remarkably strong and complicated apparatus for 
this purpose. In this class of animals the skeleton is very simple, being nothing 
more than a large branched mass of inorganic matter, which either covers its soft 
parts or supports them, and varies exceedingly in texture, shape, and size, accord¬ 
ing to the requirements of each particular kind of animal. The skeletons or 
organs of support of these animals are known as objects of ornament, by the 
names of Corals, Madrepores, Millepores, &c. The size to which these attain is 
sometimes very great; each of these masses must not, however, be regarded 
as the skeleton of a single animal, but rather as the work of a community. 
Although it is very difficult to say whether we ought to consider each polype 
as an entire animal, yet on account of the facility with which they are enabled 
to maintain an independent existence, the collected masses have generally been 
considered as an aggregate of animals. These animals generally inhabit the 
depths of the ocean, where the branched forms of their organs of support, and the 
varied colours and shapes of their tentacula, give them the appearance of a forest 
of trees. In fact it is not yet a hundred years since naturalists mistook many 
of these curious animals for plants ; and even now they bear a name, zoophytes, 
which would indicate that they belong both to the animal and vegetable king¬ 
doms. These animals exist in such enormous numbers at the bottom of some 
seas, that the collections of matter forming their skeletons are often brought almost 
to the surface of the ocean, w T here they form formidable reefs that frequently seal 
the fate of the unwary mariner who navigates his bark upon their unseen 
summits. But more than this, these reefs are sometimes thrown above the level 
of the sea by volcanic or other changes, and thus these animals have been supposed 
to be the chief agents employed by the Creator in forming those delightful islands 
scattered so abundantly throughout the Southern Sea. 
I cannot here enter into any particulars concerning all the varied forms these 
creatures assume, nor indeed of any of the other classes of animals to which I 
allude, but there is one form which, as it is so well known, I cannot but refer to. 
I allude to the Common Sponge. This is not a vegetable production, as often 
supposed, but is the organ of support or skeleton of an animal belonging to this 
class. It differs from those I have just mentioned in not possessing tentacula, 
and may indeed be considered as the simplest form of animal life. In all Sponges 
we find several pores or holes, the smaller of which are destined for the purpose 
of receiving the sea-water in which they live, which, being filled with animalcules, 
the Sponge appropriates them as food; and the water, thus deprived of its 
