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THE MACKAllEL TRIBE. 



Such of the Mackarcl tribe as visit or frequent the British 

 seas constitute a well-defined family, the form and habits of 

 which render them easily distinguished from all others of our 

 native fishes. They are capable of great activity, for which 

 the shape of their bodies and the distribution of their fins 

 eminently fit them, the fore part of the former being of an 

 almost conical shape, by which they are rendered well fitted 

 to make their Avay through an opposing fluid; while the 

 hindward portion is so lengthened into a rounded slope as 

 to cause the water to glide past without forming an eddy 

 that might interfere with the smoothness of their course. The 

 requisite flexibility is secured by the smooth texture of the 

 surface of the body, on Avhich the scales are so small and 

 even as to be scarcely perceptible; and in some of the sj)ecies 

 the pectoral fin is received into a depression of tlie surface, 

 where it can lie hid when a sudden and rapid rush is to 

 be made, while the most prominent of the dorsal fins falls 

 into a cavity or slit, so as to be concealed when its special 

 duties are not required. 



The tail in fishes is the great organ of propulsion, and in 

 its true nature consists of two lobes which are united in the 

 middle, but in this family with an obvious degree of separation. 

 Each of these lobes is capable of an action that is reciprocal 

 or independent of the other, by the sudden and impulsive 

 motion of which the water itself is constituted a fulcrum on 

 which each lobe of the tail is brought to bear, in the same 

 manner as with a single oar over the stern of a boat it is 

 driven onward, by what, in nautical language, is termed 

 sculling. A forked tail is better fitted to act powerfully in 

 this mode of progression than a round one, although the 

 latter may in dimensions include a larger space; and by the 

 former the influence of turning is more quickly and poAverfully 

 brought under the action of the will. Belon makes the curious 

 VOL. II. K 



