115 
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 im Barrow 
Channel. (Such a catch will be examined in the class.) 
The commoner things present in the tow-netting. 
Diatoms.—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. hey are yellow- 
green in colour. Their bodies are enclosed in hard, glass- 
hike, flinty shells. 
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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 
