Page:Natural History, Fishes.djvu/225

Rh were all taken from the same individual fish, and their number might have been much increased. 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 being 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 figures) between that part of the surface which is exposed, and that which is covered by the other scales; the concentric marks in the former