GENERAL FACTS ABOUT SEA FISH 33 



up from the uttermost depths by specially equipped scientific 

 expeditions. At the same time, a measure of distinction may 

 be permitted, sub-dividing these shallow-water forms according 

 to the depth at which they live. We can, for instance, draw 

 a line between the shore-haunting gobies {Gobius) and the 

 deeper-water halibut {Hippoglossus). This, in fact, seems to be 

 the utmost that is attained in the very interesting chapter on 

 the distribution of sea fish in Dr. Giinther's great work.* In 

 the case of non-migratory fresh-water fishes he was able, as 

 might be expected, to lay down principles and to find his 

 illustrations with almost the same facility as if he had been 

 deahng with a group of land mammals, for the salt water is 

 in all cases a bar to progress outside of the defined range, 

 even in the case of fishes inhabiting tidal rivers. So long as 

 he defined the " Fishes of Brackish Water," though there is 

 necessarily a vagueness about the limits of such a region, and 

 later the " Fishes of the Deep Sea," Dr. GUnther was fairly 

 sure of his ground, and those chapters consequently make most 

 useful reading. When, however, we come to his two inter- 

 mediate groups, the " Shore " and the " Pelagic " fishes, we find 

 continual contradictions, for it seems quite hopeless to attempt, 

 save on the broadest lines and with an infinite patience with 

 the exceptions that are certain to present themselves, any fixed 

 definition of these groups. Even with reference to the 

 demarcation between sea and fresh-water fishes. Dr. Giinther 

 himself admits that there is a constant interchange of species. 



It is only, therefore, on broad and not arbitrary grounds 

 that we may venture to distinguish between the shore-haunting 

 forms and those which live for the greater part of the year at 

 a moderate distance from the land, say outside of the ten-mile 

 limit. Even here, it will be understood even from what has 

 gone before, there is a continual mingling, for some of the 

 forms from the deeper water come inshore for spawning 

 purposes, while a still larger number will repair to the shallows 

 * A>i Introduction to the Study of Fishes, pp. 255-295. 



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