THE IMPENETRABLE SEA 



which drift or wander with the tides and currents. The 

 third division, benthos, comprises all those forms which 

 crawl over or burrow into the sea-beds, and also those 

 which are fixed in location, such as barnacles and 

 sponges. But the sea will not be tamed — not even by 

 man's classifications, so that even this "life-habit" classi- 

 fication is not definitive — the nekton, plankton and benthos 

 compartments are by no means distinct, for numbers of 

 creatures drift to and fro across the lines of demarcation 

 as though the ocean itself was determined to erode or 

 wash away arbitrary terminologies. 



Even if we attempt a simpler division of sea creatures, 

 into plants and animals, the ocean seems determined to 

 mix them. For there are plant-like animals and animal- 

 like plants. Plants often resemble animals so closely that 

 it is difficult to distinguish them, while the same applies 

 to animals which look like plants. There are seventeen 

 hundred species of the Bryozoa alone. The name means 

 "moss animals", and they are to be found in their 

 myriads : moss-like and lichen-like creatures attached to 

 the rocks, stones and pebbles of the world's sea-coasts; to 

 pieces of seaweed and other natural growths, and to the 

 shells of crabs, lobsters and other crustaceans. 



The phrase "a fish out of water" is often used to 

 describe a state of discomfort among incongruous or 

 unnatural surroundings. It can, of course, be used with 

 reference to the majority of fishes if any of them are 

 taken out of their element, and even with regard to those 

 which make occasional visits to the surface or brief flights 

 above it : they cannot live out of the sea for long : they 

 must soon die unless they return to the waters. Yet there 

 are some sea creatures that seem anxious to get out of 

 the water, and which live much of their lives away 

 from it. 



Among them are the mud-skippers, which inhabit the 

 river mouths of various parts of Africa, Asia and Aus- 

 tralia. 



112 



