248 On the Scales of Fishes. 



(Pleuronectidce) , is rarely seen •with a scale on it, while others 

 retain them firmly, and again others of the same family are not 

 possessed of any. The anchovy loses its scales so readily, that 

 Belon, who was an observant naturalist, believed it to be 

 without them. The herring also, and pilchard, will lose them 

 without much violence, but the shads, which are of the same 

 family, retain them rather firmly. But whether held loosely or 

 firmly, in every case the scales of a fish are clothed to their 

 free borders where there are such, with the common skin, of 

 which a duplication is carried over that border to the lower 

 surface, so far as it remains free ; by which it is arranged that 

 each scale becomes enclosed within a case or cell, of which the 

 anterior border is overlapped by the next preceding one, and 

 the firmness with which it is held depends chiefly on the 

 extent to which it is thus overlapped. The cuticle which 

 covers the more exposed and looser portion of the scale is 

 sometimes exceedingly thin, and therefore feeble ; but it is the 

 portion of the surface which furnishes the colour, and from 

 which, in some degree, the substance of the scale obtains its nou- 

 rishment and growth, although this latter is chiefly from a lower 

 and less coloured portion of the case or cell. In some instances 

 the scale itself, and also its covering skin, are so transparent, 

 especially in individuals of early growth, that an exudation 

 and deposit beneath it becomes conspicuous through its sub- 

 stance, of which we shall produce some examples. But the 

 growth or expansion of a scale, as the fish advances in size, is 

 the more material property of its nature ; and this, on close 

 examination, will be found to have its source of nourishment 

 and increase from about the middle of its surface, and from 

 which it spreads itself on all sides, although in a greater 

 degree to its free edge and its root, which latter lies forward 

 in the direction of its body. It is at about this middle portion 

 of the scale, but varying a little in situation in different species, 

 that we discover an organized disk, into which, as wc can per- 

 ceive in the larger scales of fishes, there are vessels inserted, and 

 those not always of a very minute size ; but those that pass to 

 each surface of a scale may be distinguished from each other, as 

 well in arrangement as capacity ; and it is from this circum- 

 stance we draw the conclusion that the scale itself consists of 

 a double layer, like that of the nail of the human finger and 

 toe ; although, in the generality of instances, the structure is 

 too fine to allow of our obtaining a positive proof of the 

 fact. 



The examples which will be selected for description will 

 illustrate these remarks ; but although there is a general 

 resemblance in the marking of the scales of each species, 

 the outline of their shape is found to vary much according 



