GREA T BRITAIN. 85 



short tortuous lines, the scribbled mackerel ; while a third is 

 marked over with spots and dots, and known as the dotted 

 mackerel ; all intermediate forms of colour between these 

 several varieties have been found. Mr. Dunn has likewise 

 mentioned that some red-finned varieties exist which the 

 fishermen carefully look for, because on their appearance a 

 plentiful supply is usually off the coast. Disease may like- 

 wise change the shape of the bodies of these fish ; thus in 

 some forms the vertebral column is twisted into various 

 shapes due to disease ; or there may be disease of the 

 oviducts, occasioning an occlusion, and so preventing the 

 eggs being extruded ; round these a cyst forms, and when 

 the next season's eggs begin to grow, the shape of the 

 fish becomes entirely altered, being much deeper than 

 natural. 



Habits. Mackerel are a gregarious, wandering, pelagic 

 form of fish, which remains off our coasts throughout the 

 year, and at certain seasons approaches the shores in count- 

 less multitudes, prior to, during, or subsequent to breeding ; 

 this may, and evidently sometimes is, due to the food they 

 are in pursuit of, or the temperature of the water. Oc- 

 casionally they forsake their usual haunts ; thus from May 

 to July they were formerly abundant off Yarmouth and at 

 Lowestoft, whereas now numbers arrive with the herrings, 

 having deferred their advent to a rather later period of the 

 year, or they may antedate their arrival, as has been 

 observed in some localities. Formerly they were supposed 

 to undertake annually long migrations from the north 

 towards the south at one season, and subsequently the 

 reverse. Lacepede, on the authority of Admiral Pleyville- 

 Lepley, actually asserted that in some small and almost 

 land-locked bays off Greenland, where the water is always 

 clear, and the bottom consists of soft mud, myriads of 



