GREA T BRIT A IN. 5 5 



seems likewise very probable that the screws or paddles of 

 steamers may prove destructive to a considerable amount 

 of the eggs and fry of surface fishes. As to the predaceous 

 fishes and other animals which are detrimental to fisheries, 

 they will be alluded to when describing the different 

 species. 



Fish are likewise much affected by parasites ; some of 

 these are external and attack the surface, as fish lice ; they 

 can move from place to place and select some suitable spot 

 where they fix themselves by means of their hooked and 

 prehensile antennae. Others are more sedentary, frequently 

 having their heads deeply buried in the body or tissues of 

 its victim. Having no powers of locomotion, the whole of 

 their external organs are often merely rudimentary. They 

 are seen in the eyes, gills, roof of the mouth, nostrils, vent, 

 skin, and on the fins. Some forms, again, are internal and 

 attack any of the internal organs of the host which they 

 afflict with their presence. 



Fish may be employed as food either fresh or cured ; 

 while the latter embraces such as are dried either in part 

 or wholly, or pounded, and then dried in the sun, shade, or 

 by artificial means ; or smoked partially or wholly, salting 

 or drying being used or abstained from ; or salted either 

 dry or in pickle in various ways, while sugar may be em- 

 ployed in the place of salt ; or preserved by the exclusion 

 of air or with the assistance of acids ; or by keeping the 

 fish by means of natural or artificial cold at a temperature 

 below that at which fermentation or decay sets in. 



The geographical distribution of our fishes has been more 

 or less examined by various naturalists whose views have 

 not invariably been in accord one with- another. Certain 

 terms have been instituted partly to convey to the worker 

 an insight into the habits and distribution of this class of 



