THE SCOMBER SCOMRRUS. 225 



marine insects. According- to Admiral Le Pleville le Peley, 

 they have been observed by him in severe winters, and even 

 to the commencement of spring, about the coasts of Green- 

 land and Hudson's Bay, at the bottom of the small clear 

 hollows, encrusted with ice round the coasts, entirely bristled 

 over with the tails of the mackerels, whose heads were im- 

 bedded in the fine soft mud at the bottom, to the extent of 

 more than three inches, in some even to three parts their 

 entire length, being thus protected sufficiently from the 

 severe effects of the frost ; and on the return of the spring, 

 they are generally believed to migrate in enormous shoals, 

 of many miles in length and breadth, to visit the coasts of 

 more temperate climates, in order to deposit their spawn. 

 Its route has been supposed to be similar to that of the 

 Clupea Harengis or common herring, passing between Ice- 

 land and Norway, and proceeding towards the northern 

 parts of Scotland, the Orkney and Shetland Isles, where a 

 part of the shoal throws itself oft' into the Baltic, whilst the 

 o-rand column passes downwards and enters the Mediter- 

 ranean Sea, through the Straits of Gibraltar. 



This Ions' migration of the mackerel, as well as the her- 

 rino-, seems at present to be greatly called in question ; and 

 it is considered as more probable that the shoals which ap- 

 pear in such abundance round the more temperate European 

 coasts in reality reside during the winter at no very great 

 distance, immersing themselves in the soft bottom, and re- 

 maining in a state of torpidiiy, from which they are awak- 

 ened by the genial warmth of the returning spring and 

 gradually recover their former activity. At their first ap- 

 pearance their eyes are observed to appear remarkably dim, 

 as if covered with a kind of film, which passes off as the 

 season advances, when they appear in their full perfection 

 of colour and vigour. 



The general length of this species of the mackerel is from 

 ten to sixteen inches, but in the Arctic Seas it is occasionally 

 found of far greater size, and, amongst those which visit our 



Q 



