DEVELOPMENT OF THE SCALES AND BONES OP FISHES. 
647 
The first scale to which I would direct attention is a very large one from the Bay 
of Dulse, on the western coast of Central America, and for specimens of which I am 
indebted to Sir Philip he Malpas Grey Egerton, Bart. I have not been able to 
learn the name of the fish to M'hich it belongs, but from its large size, it furnishes 
such a beautiful illustration of the internal structure of this class of scales, that not- 
withstanding my ignorance of its name I avail myself of the information which it sup- 
plies ; its natural size, and the aspect of its upper surface are represented in Plate 
XXVin., fig. 1 . It is of the Ctenoid type, but one of those examples which approaches 
very closely to the Cycloid form. Fig. 1 a is its posterior, and 1 b its anterior margin; 
each of which respectively present some peculiarities of structure. A few concentric 
lines are seen on various portions of its upper surface, which exhibits to the naked 
eye a frosted appearance, like that given to the vegetation by the hoar-frost on an 
autumnal morning. Posteriorly and laterally, bundles of divergent lines ornament 
this surface ; they proceed somewhat irregularly, from near the centre towards the 
margin of the scale, being small grooves in its uppermost layer, which correspond 
with the canals” of M. Mandl. 
On making a vertical section of this fine scale along the line fig. I, a, b, we obtain 
the structure represented in fig. 2, portions of which, still more highly magnified, are 
shown in figs. 3 and 4. We at once see that not only is the membranous lower layer 
(figs. 3 a and 4 a) distinct from the calcareous one, but that the lattei’ portion consists 
of two distinct structures; a superficial (3 c and 4c) and an intermediate one {3 b 
and 4 b). Fig. 3 represents a portion of the section (fig. 2) as seen at a, but viewed 
under a magnifier of still higher power. Interiorly, it consists of numerous mem- 
branous laminoe (3 a) arranged in parallel horizontal lines. We learn from fig. 2 that 
these laminae are most numerous in the centre of the scale, and diminish in number 
as we approach its margin, until we arrive at the extreme periphery, where but one 
exists. This is partly shown in fig. 4, which represents the portion of the section, 
fig. 2, as seen at b, but more highly magnified. We here see (4 a) the same mem- 
branous lamellae as in fig. 3, only diminished in number and thickness, and which 
successively run out as we approach the margin of the scale. This margin is not quite 
reached at 4 f, but nearly so, since we find that the number of the visible membrani- 
forin laminae is reduced to two. 
Each of these membranous laminae consists of numerous hair-like fibres, all those 
entering into the composition of one lamina being arranged in parallel lines; fig. 5 
represents the horizontal aspect of portions of two such laminae, showing the diagonal 
manner in which the fibres of each are arranged. The detached fibres seen at fig. 5 a 
exhibit a marked tendency to curl up in the way that those of the yellow fibrous 
tissue (ligamentum nuchae) of mammals are well known to do. 
Imbedded amongst these membi'anous laminae, we see numerous isolated, lenticular 
calcareous bodies (figs. 3 d and 4 d), each of which exhibits a definite series of con- 
centric lamellae, with traces of a central longitudinal fissure. These small bodies have 
4 0 2 
