THE LIFE-HISTORIES OF FISHES 175 



actually in, the mud and sand forming the bottom 

 deposits. In such species gill-rakers are not re- 

 quired, and are absent, for the food consists of 

 comparatively large animals, such as small shell-fish 

 like mussels (in the case of the plaice), or worms 

 (in the case of the sole). These animals live in 

 the mud or sand, and are caught individually and 

 swallowed by the fishes. The fishing apparatus 

 adopted for the capture of these latter species is 

 the trawl-net, which sweeps along the sea-bottom, 

 or hooks fastened to long lines, which also lie on 

 the sea-bottom. 



I have given here only the barest summary of 

 the principal classes of facts relating to the natural 

 history of marketable fishes, and will again refer 

 the reader to the abundant literature which deals 

 with the subject. Although our knowledge is 

 still very far from being complete on this head, 

 yet so many investigations have been made during 

 the last twenty-five years that we have now a 

 very fair notion of the principal facts in the life- 

 history of fishes. The subject is one of very 

 great interest, and the reader who is interested 

 generally in sea-fishery investigations may very 

 profitably pursue it further. 



