RADIATA. 509 
and they appear to partake of the nature of stones, vege- 
tables, and animals. 
Sponge is a substance of a soft, light, porous, and elastic 
nature, which is found adhering to rocks at the bottom of 
the sea, in several parts of the Mediterranean, and parti- 
cularly near the islands of the Grecian Archipelago ; and 
which, in its native state, is filled with animal jelly. The 
general uses of Sponge, arising from its ready absorption 
of fluids, and distension by moisture, are well known, 
and of great importance. It is collected from rocks, in 
Avater five or six fathoms deep, chiefly by divers, who, 
after much practice, become extremely expert in obtain- 
ing it. When first taken from the sea, it has a strong 
and fishy smell, from the animal matter it contains, and 
of which it is divested by being washed in clear water. 
No other preparation than this is requisite previously to 
its being packed up for exportation and sale. The growth 
of Sponge is so rapid, that it is frequently found in per- 
fection on rocks, from which, only two years before, it 
has been entirely cleared. 
THE LONG-ARMED, AND THE FRESH-WATER 
GREEN POLYPES. (Hydroida.) 
THESE are two species, which will fully illustrate the 
nature of the whole tribe. They are found in clear waters, 
and may generally be seen in small ditches and trenches 
of fields, especially in the months of April and May. 
They affix themselves to the under-parts of leaves, and 
to the stalks of such vegetables as happen to grow im- 
mersed in the same water; and they feed on the various 
species of small worms, and other aquatic animals that 
happen to approach. When an animal of this kind passes 
near a Polype, the Polype suddenly catches it with its 
arms, and dragging it to its mouth, swallows it by de- 
grees, much in the same manner as a snake swallows a 
