272 THE LIFE OF CRUSTACEA 



of sea-water for examination with a lens or under the 

 microscope. 



Dredging is the most effective method of obtaining 

 Crustacea that hve in deeper water. The dredge 

 usually employed by naturalists consists of a heavy 

 rectangular iron frame to which is attached a strong 

 bag-shaped net. The two longer sides of the frame 

 are sharp-edged and bevelled outwards, so as to 

 " bite " when the dredge is dragged along the sea- 

 bottom. To the shorter sides are hinged a pair 

 of arms ending in rings. The dredge-rope is made 

 fast to one of these rings, while the other is held 

 only by a "stopping" of yarn, which gives way if 

 the dredge should catch on a rock, and permits it 

 to be dragged sideways off the obstruction. The 

 size and weight of the dredge may vary according 

 to the depth at which it is to be used and the power 

 available for working it. A convenient size for use 

 with a small sailing boat at moderate depths has 

 a frame 20 by 5 inches. 



Apart from dredging, many specimens from 

 moderately deep water may be picked out from 

 among the " rubbish " brought up on fishermen's 

 lines or by the trawl, and various Crustacea besides 

 the edible species find their way into Lobster and 

 Crab pots. The true deep-sea fauna is, for the most 

 part, only to be reached by specially-equipped ex- 

 peditions, although specimens from great depths are 

 occasionally obtained during the operations for the 

 repair of submarine telegraph cables. 



The floating animals of the surface of the sea are 



