HOW SPONGES LIVE. 35 
delicately ? \Yhat architect has laid the fibres so 
skilfully, and formed such a wonderful and intricate 
structure ? 
The architect is one of Life's children, whose his- 
tory we must next consider ; for though the sponge 
was long thought to be a plant, we now know that 
it is the skeleton or framework of a slime -animal, 
a little higher than those spoken of in the last 
chapter. When the sponge which you hold in your 
hand was alive, growing on the rocks in the \varm 
deep waters of the Grecian Archipelago or the 
Red Sea, it did not consist merely of the soft fibre 
you now see, but was covered all over the outside 
and lined throughout, even along the smallest of its 
tubes, with a film of slime. This slime, though it 
appears to be all one mass with specks of solid matter 
here and there, is really made up of Amoebae or finger- 
slime beings (see Fig. 2), and if any little piece is torn 
off it floats in the water and puts out fingers, exactly 
as the Amoeba does. Nevertheless, in the sponge 
all these separate cells are not independent creatures, 
but form the flesh of one single sponge -animal, 
which lives, breathes, feeds, grows, and gives forth 
young ones in its ocean home. 
At the bottom of the warm seas on the Mediter- 
ranean coast or in the Gulf of Mexico these sponge- 
animals live in wild profusion, sometimes hiding in 
submarine caverns, sometimes standing boldly on the 
top of a slab of rock, or often hanging under ledges. 
Some are round like cups, some branched like trees, 
some thin and spread out like a fan ; while there is 
scarcely a colour from a brilliant orange to a dull 
dingy brown, which is not to be seen among them. 
