The Zoophytes. 309 
slopes below the reach of the tides. The floating forms 
are the familiar jelly-fishes, while the immense variety of 
the fixed colonies, bear the names of objects which they 
resemble in miniature, such as sea-fir, sea cypress 
etc.; and while those with harder and firmer skele- 
tal parts are generally distinguished as corals and 
sponges, the smaller and more delicate Hydroid 
Zoophytes are commonly taken for and ranked with 
sea-weeds. 
Though of a very simple grade of organisation, yet 
the Zoophytes play a considerable part in nature. They 
furnish continuous supplies of food to a very large 
number of marine organisms ; under the form of sponges, 
their skeletal tissues are of considerable practical impor- 
tance and form the basis of a very extensive industry ; 
while the abundant formations of coral both in ancient 
geological times and in the present day, give a special 
significance to the task assigned to them by Nature, in 
the building up of sub-marine peaks and their trans- 
formation into terrestrial areas, which in time become 
suitable for the support of the higher forms of animal 
and vegetable life — a task which has resulted in the pro- 
duction of numerous inhabited areas situated in the 
tropical portions of the globe. 
The Zoophytes are typically marine organisms, though 
many forms are to be found in brackish water, and a 
few have entirely taken up their abode in perfectly 
fresh water. Of these last, the common Fresh-water 
Polyp (Hydra) , the rare and unique Fresh-water Medusa 
(Limnocodium.) lately discovered in the tank of the 
Victoria regia in the Royal Botanic Gardens of London, 
and the Fresh-water Sponge (Spongilla) may be men- 
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