28 THE EXPLORATION OF THE SEA [PART I 



forwards and downwards, and is fixed in this position by wire 

 stays. The whole is towed by six wire bridles bent to the usual 

 rope. The inclined board gives the whole net a sheer downwards 

 whereby it fishes in the deeper layers of the sea even near to the 

 bottom, or by suitable management at any required depth. Its 

 comparatively wide mesh and its easily controlled position make it 

 an instrument of the greatest value for fishing for the larvae and 

 young stages of fish, or indeed for many other organisms of larger 

 size than those usually caught by the ordinary tow-net. 



Then we have the various modifications of the otter trawl 

 devised by the Heligoland, Norwegian and Danish naturalists. 

 I leave the reader to puzzle out for himself the synonomy of these 

 instruments. One is a long conical bag of hempen net which is 

 bent on to an iron ring. The net is about 5^ metres long, and the 

 diameter of the ring about 2^ metres. It is towed by three bridles 

 and a steel rope, and is kept at the surface or at any depth by 

 a float. A modification of this apparatus is a larger net conical 

 in shape, with a rope ring to keep it open, to which are attached 

 three otter boards from which three bridles pass to a steel warp. 

 These three otter boards keep the mouth of the net open so that 

 the opening is a triangular one of about 50 to 100 square metres. 

 The length of the net is about 30 metres. 



Finally we have the young fish trawl used by the Danes. 

 This is a pelagic otter trawl difi'ering from the parent instrument 

 mainly in its size and in the fineness of the mesh, which is adapted 

 to catch organisms of the size of very young fishes. All these 

 instruments differ from the old tow-net (1) in their greater size, 

 (2) in their wider mesh whereby they are enabled to catch the 

 larger planktonic animals, and (3) in the ease whereby they can 

 be made to fish at different levels in the sea. Some consideration 

 of the literature of the International Fishery Investigations will 

 shew that it is by means of these instruments that very important 

 additions to our knowledge of the life histories of fishes have been 

 made, additions that we should probably still be waiting for had 

 we possessed only the old tow-nets as means of investigation. 



All the fishing apparatus I have described are to be character- 

 ised as qualitative apparatus, adapted onl}^ for the purpose of 

 ascertaining the presence and distribution of marine organisms. 



