65 
THE MACKAEEL TRIBE. 
Such of the Mackarel tribe as visit or frequent the British 
seas constitute a well-defined family, the form and habits of 
whmh 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 way through an opposing fluid; while the 
landward 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 which the scales are so small and 
even as to be scarcely perceptible; and in some of the species 
the pectoral fin is received into a depression of the 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. 
Ihe 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 powerfully 
brought under the action of the will. Belon makes the curious 
VuL. II, K 
