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TRANSACTIONS LIVERPOOL BIOLOGICAL SOCIETY. 



the "shear" plate exactly as on the otter boards of fche 

 otter trawl, or like the wind on a " kite," causing, in this 

 case, the net to sink in the water. Knowing the length 

 of rope allowed to run out, the true depth of the net can 

 be easily found by using the Apstein apparatus already 

 described and measuring the angle the rope makes with 

 the horizon. 



A still larger net than the " Brut " net is sometimes 

 desirable where very large catches are required of the 

 larger plankton forms from deep water. For this purpose 

 there is the so-called " Kniippel " net (fig. 6), which is 



H 



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Pig. 6. — The "Kniippel" net. 



worked on the principle of the otter trawl. The Kniippel 

 net can only be worked satisfactorily when a fair sized 

 vessel is available with a steam winch. The net which 

 I have seen in use has the following dimensions. The net 

 itself is made of strong canvas and is about 15 to 20 feet 

 long, the mouth is square, each side of the square having 

 a length of 8 feet, and each of the mouth edges is formed 

 by a broad piece of sailcloth, to which the filtering canvas 

 is sewn. The apex of the net is as usual fixed to a metal 

 bucket, in this case about 9 inches in diameter. The 

 two vertical sides of the mouth of the net are fixed at 

 intervals to two stout poles (fig. 6, h. and c.) 9 feet long, 

 and provided at the lower end with a heavy lead sinker 



