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- 



