34 THE STORY OF LIFE IN THE SEAS. 



them seem to be perfectly satisfactory, and con- 

 sequently it is unnecessary to enunciate them in 

 detail in this small book. 



The character of the bottom of shallow water, 

 especially in the neighbourhood of the coasts, 

 presents us with so many variations that it would 

 be a long task to consider in detail all the differ- 

 ent adaptations that the animals exhibit. The 

 Fauna of the sand, shingle, and mud at the 

 mouths of rivers, of the rocks of iron-bound 

 coasts, and of the coral-reefs, each present us with 

 many curious kinds of modification of form and 

 structure. A brief reference to one or two 

 characteristic regions must be made before pass- 

 ing on. 



The sandy bottoms which are so prevalent, 

 not only upon our coasts, but in nearly all 

 parts of the world, invariably support a Fauna 

 with many curiously altered forms. In walking 

 across the sands at low water we may have often 

 noticed many worm-like and twisted columns of 

 sand ; these are the casts of the common Lug- 

 worm, which is a favourite bait for many kinds 

 of Fish. The Lug-worm lives in a U-shaped 

 tube, which it forms from a slimy secretion of the 

 body ; it feeds by swallowing the sand in which 

 it burrows, extracting from it as it passes through 

 the intestine whatever animal or vegetable food it 

 may contain. There can be little doubt that the 

 sand is a very poor form of diet, and that an 

 immense quantity must pass through the body 

 of the animal compared with its weight in order 

 to afford sufficient nourishment. It has been 

 reckoned that as many as 82,433 casts may be 



