MIGRATION. 89 



10. And we also may ask, " Why the smallest herrings 

 proceed to certain places in the Baltic, and the larger to 

 the North Sea ?" and as it is asserted that the whales are 

 the cause of their flying south, why do we not see the 

 whale on every coast every year ? Mr Yarrell, in his 

 valuable work on fishes, truly says : " There can be no 

 doubt that the herring inhabits the deep water all round 

 our coast, and only approaches the shore for the purpose 

 of depositing its spawn within the immediate influence 

 of the two principal agents in vivification, increased tem- 

 perature and oxygen ; and as soon as that essential opera- 

 tion is effected, the shoals that haunt our coast disappear, 

 but individuals are to be found, and many are caught 

 throughout the year" (vol. ii. p. 112). 



11. Various other fishes have similar habits in spawn- 

 ing. The salmon ascends rivers from the sea at parti- 

 cular periods for the purpose of spawning. The sprat 

 appears in shoals, in various localities of the coasts of the 

 British islands, from November to March. The shad or 

 alosa is found in shoals in some of our rivers from May to 

 July : in the Severn generally in May, and it continues 

 there about twomonths; in the Mediterranean, near Smyrna 

 and Eosetta ; and it ascends the Nile as high as Cairo in 

 December and January. The pilchard appears in shoals 

 on the coast of Cornwall, from June to the end of the 

 year ; and the tunny comes in-shore on the coasts of the 

 Mediterranean in summer. All these fishes appear to 

 have the same habits of gregariously visiting various 

 coasts and rivers at particular seasons, for a similar pur- 

 pose ; but no one would on this account pronounce them 

 natives or inhabitants of a distant quarter of the globe. 



In short, from all the circumstances known of the 

 natural history of the herring, in regard to its visits on 



