THE DENSITY OF ANIMALS ON THE OCEAN FLOOR I97 



Swinging the Petersen grab on to the deck. Emptying the grab. 



Sifting the sample. 



waters can be divided into regions, each dominated by a few different 

 species. A region such as this is termed an animal community and is named 

 according to the small animals which predominate in it. From the Euro- 

 pean coastal waters explored a whole series of these animal communities 

 has been described. 



Such quantitative samplings of the composition of the bottom fauna 

 had hardly ever been made outside northern European and Greenland 

 waters, and never in the deep sea. It was one of the special objects of 

 the Galathea Expedition to do this, and with our wide experience of the 

 Petersen grab it was felt that we were exceptionally well equipped for 

 the work. According to our instructions, our principal field of operations 

 lay in the great ocean deeps, and particularly in depths beyond 4,000 

 metres. However, an exception was made as regards quantitative bottom 

 sampling. This we were also to carry out in shallow water, so that, by 



