THE GREAT DEEPS 123 
tactile organ seen hanging down for about an 
inch from the front of the cod’s lower jaw. 
Another fitness is the delicate build of the 
body—such as we see in Venus’s Flower 
Basket (Euplectella), whose flinty skeleton 
rises like a fairy palace from the floor of the 
deep sea. When the sponge is living, the 
beauty of the skeleton is hidden by the tissues, 
and the significance of the skeleton to the ani- 
mal is that it forms a scaffolding for lifting 
a fairly big body—sometimes about 2 feet 
high—off the floor of the sea. The scaffold- 
ing is so delicate that the weight of a child’s 
hand crushes it, and yet it is more effective 
than a solid bone would be to resist the enor- 
mous pressure of the water—many tons on the 
square inch. It circumvents the pressure, for 
when the water gets through and through an 
animal the pressure inside and the pressure 
outside are equal. The same applies to the 
Glass-Rope-Sponge (Hyalonema), which is 
raised on a long stalk of flint fibres, always 
bound together by a colony of anemones. The 
theory of the adaptation to outside pressure 
becomes more difficult when we pass to ani- 
mals with a body-cavity, a food-canal, blood- 
vessels, and so on, but the general theory re- 
