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TRANSACTIONS LIVERPOOL BIOLOGICAL SOCIETY. 



dimensions and a filtering surface of very large area. The 

 cubical capacity of the net is also as small as possible, so 

 that when it is hauled up it is unnecessary to wait so long 

 for the water which remains in it to filter through. It is 

 also easy to unfold the net, to wash out its contents, and 

 replace it in the metal covering. In order to increase 

 the surface of a net either its length or its circumference 

 can be increased. Hensen at first tried pushing in the net 

 on itself, in a similar manner to that in which the finger 



Fig. 11. 



of a glove can be pushed in. This form was given up 

 because the net was inconveniently long and the end very 

 narrow. The case might be made square and the surface 

 increased by deep foldings, so that the surface resembles 

 a photographic camera. This form would be very con- 

 venient and practicable if the net could always be 

 arranged in such folds. A spiral arrangement of the net 

 appears impracticable, therefore the net has been folded 

 in the direction of its longitudinal axis, as was done by 

 Hensen for his cvlinder net (4, p. Ill), but with the 

 modification that the net lies in a basis that can be fully 

 withdrawn from the metal covering. 



