On tJie Scales of Fishes. 249 



to the part of tlie body from which they are taken. Those 

 which clothe the back, and especially nearest the head, 

 are the smallest, and they are often oblong and crooked ; and 

 those along the line of the belly, especially in the pilchard and 

 sprat, are of singular shape. Our examples, therefore, as 

 offering the best illustrations of the growth and character, are 

 taken from the side, where the outline is the most regular and 

 the structure most easily discerned. In general, the scales of 

 the lateral line are nearly alike in each family, but with a 

 subordinate variation that renders them in some degree peculiar 

 to the individual species, as we shall notice in the common 

 sea-bream, Pagellas Gentrodontus. The special purpose of the 

 structure which so generally marks the scales of the lateral 

 line is to secrete and pour out a peculiar fluid, that is intended 

 to lubricate the general surface, so as to enable the fish to pass 

 the more smoothly through the water, and perhaps also to 

 secure it from any ill effect of the fluid in which it swims ; and 

 it is observed that this mucous does not speedily diffuse itself 

 amidst the surrounding water. Those fishes which have few 

 or no marks of this structure in a lateral line, or which seem 

 to require an additional supply of this lubricating fluid, are also 

 provided with additional pores about the head and mouth for 

 the same purpose. 



Of the scale of the perch, Perca fluvialilis, a representa- 

 tion is to be found in the work " Microscope Teachings," 

 PL V., and also of the sole, Solea vulgaris. The scales of 

 the perch are of good size in proportion to that of the fish, for 

 the most part wider than long, with a disk rather obscurely 

 marked, more than three-fourths of the length towards the 

 free edge, and from which pass backward toward the covered 

 portion or roof five or six lobes, of which those toward the 

 border are the widest ; those in the middle narrow, with their 

 narrowest portions meeting close together at the disk, and all 

 of them showing separating marks of growth. At the free 

 edge are short fine points, from each of which passes back to 

 near the disk a line, of which each is marked with a cross line 

 in succession, as if each had advanced by successive starts of 

 progress. This disk, therefore, appears to form the centre of 

 all its growth, as well in regard to length as breadth, as we 

 shall see it does in every other instance, and conspicuously in 

 that of the Scioenae (8. Aguila). The scales of this latter 

 fish are large, so that in a full-grown example one of them 

 would cover a florin ; but in their shape, or on different parts of 

 the body, they vary more than in most of our native fishes. 

 Many of them taken from one fish appear as if they had been 

 injured, and had recovered the injury as by some natural 

 process of vitality. The disk, which is slightly nearer the free 



