HAIRS, FEATHERS, AND SCALES 33 



the last (/) from the throat. Thus we see there is consid- 

 erable variety in form presented by the scales even of the 

 same individual fish. They all, however, differ from those 

 of the Perch in this respect: that their free overlapping 

 edges are entire, or destitute of the crystalline points which 

 we saw in the former examples; while they agree in having 

 the front edges, by which they are during life imbedded in 

 the skin, cut into waves or sinuosities. The lower part, as 

 we now look at them, is the free portion of each, which 

 alone is visible in the living fish, the other parts being 

 concealed by the three neighboring scales that overlap it 

 above, in front, and below. 



In those from the lateral line, the tube already referred 

 to is seen to pervade each, running through it longitudi- 

 nally, so that it opens posteriorly on the outer surface, and 

 anteriorly on the inner or under surface of the scale. In 

 the scales near the front of the line, just behind the head, 

 the tube is large and prominent (a), while in the scales 

 at the opposite extremity it becomes slender; diminishing, 

 in the very last scale viz., at the commencement of the 

 tail-fin to a mere groove. 



The whole surface of each scale, when viewed under a 

 lens of low power, is seen to be covered with concentric 

 lines, following the irregular sinuosities of the outline. 

 These lines are the edges of the successive layers of which 

 the scale is believed to be composed, each layer being added 

 in the process of growth to the under surface, and each be- 

 ing a little larger every way than its predecessor; thus the 

 scale is a very depressed cone, of which the centre is the 

 apex. There is a marked difference (indicated in the fig- 

 ures) between that part of the surface which is exposed, 

 and that which is covered by the other scales; the concen- 



