2i8 Ova in the sea. Chapt. xvi. 



ova, which float, to be hatched on the surface, some in 

 the sand, some among the rocks and sea-weed. 



As a general rule the ova of fresh-water fish sink to 

 the bottom, and the ova of sea-fish float. It is a wise 

 provision that it is so. The ova of river-fish require to 

 reach the bottom to prevent their being washed down by 

 the stream, that would otherwise soon carry them to the 

 salt water and destruction. If the ova of sea-fish similarly 

 sank, they would, at the bottom of the deep sea, lose the 

 life giving influences of that heat and light which they 

 gain by floating on or near the surface. 



Remembering this great leading fact, and remember- 

 ing also another matter in connection with the sea which, 

 though well known, we are apt to lose sight of in connec- 

 tion with sea-fisheries, I think we are in a fair way to 

 discover the causes which govern the migrations of cer- 

 tain sea-fish. We are accustomed to look upon the sea 

 as one vast pond of still water, differing only from other 

 ponds in being salt, in having tides, and in being more 

 moved by winds than other ponds or lakes, by reason of 

 its having a larger surface exposed to their influence. 

 We are not ignorant, by the way, that there are currents 

 also, and that there is one mighty one called the Gulf- 

 stream, and -we can understand mariners having to know 

 something about them; but that they should affect fisher- 

 ies is not I think commonly considered. So many and 

 various however are the sea currents, that it would be 

 a much more accurate starting point for thought, if we 

 looked upon the ocean as an agglomeration of vast salt- 



