SEA-FISHERIES LABORATORY. 



195 



with 100 or more meshes to the inch. It is towed slowly 

 behind a boat, and when it is fished the catch is shaken 

 out into a bottle of clean water. 



Examination of a tow-netting taken in Barrow 

 Channel. (Such a catch ivill be examined in the class J 



The commoner things present in the tow-netting. 



Diatom s. — These are very small plants, some of 

 which live in the sand and mud at the sea bottom, but 

 most of which float about in the sea. They are yellow- 

 green in colour. Their bodies are enclosed in hard, glass- 

 like, flinty shells. 



1 



Diatoms. — 1 and 2 are floating diatoms, but 3 to 6 live 

 at the bottom. All highly magnified. 



Diatom Ooze . — In some parts of the sea far 

 away from land and in very deep water (about 2,000 

 fathoms) the mud at the bottom is soft and white, and 

 when it is examined with the microscope it is seen to 

 consist of nothing but diatom shells. These little plants 



