LIFE AT AND NEAR SURFACE 127 



' Moreover, they are constantly dying and 

 their skeletons are ever sinking slowly to the 

 bottom of the sea and for some 50° north and 

 south of the equator and at depths up to 

 two thousand four hundred fathoms, the 

 bed of the ocean is largely composed of their 

 shells. This formation is known as "Globi- 

 gerina Ooze" or "Foraminiferous Ooze," and 

 in many places it forms a large part of the 

 -so-called "sand-banks" which block harbours 

 and channels. 



This ooze would be just as thick throughout 

 the entire bed of the ocean were it not for the 

 fact that at great depths the tiny calcareous 

 shells are dissolved. All the dead and decay- 

 ing animal matter also sinks slowly down in 

 the sea, but in the dark, cold water it decom- 

 poses very gradually and in many places it 

 forms a thin, slimy layer of a gelatinous sub- 

 stance which for many years puzzled scien- 

 tists. At first it was thought to be a special 

 organism, created for the sole purpose of pro- 

 viding food for deep-sea life, but it is now 

 known to be nothing more nor less than de- 



