DEVELOPMENT OF THE SCALES AND BONES OP FISHES. 
665 
soliclated portions of tlie respective vertical laminae, and correspond with 24 d. 26 b, h 
are their inner and more lax portions, corresponding with 24 e. These vertically 
disposed tissues are traversed by the numerous horizontal bundles of fibres, 26 c, 
which proceed, as already described, towards the periphery of the scale. Whilst the 
flattened portions of the latter pass through the meshes of the dense outer tissues, 
24 d and 26 a, their more contracted and cylindrical parts traverse the inner and 
looser textures of the corresponding laminae, 24 e and 26 h. 
At their inner extremities, nearly all these latter bundles of fibres appear to ter- 
minate along lines which correspond with the radiating calcareous septa, fig. 18 e, 
but in reality they are only deflected in the direction of these lines towards the 
centre of the scale. A reference to the corresponding direction of the kosmine canals 
in fig. 18 will render this point intelligible. 
After decalcification, we are no longer able to identify either the vertical or horizontal 
laminae which were originally calcareous ; their membranous portions have evidently 
no peculiarity of structure distinguishing them from those which were not calcified. 
We thus find that all the various complicated tissues existing in the lower portions 
of this curious group of scales, consist primarily of but two sets of fibres, running in 
different directions. The same arrangements exist in the decalcified scales of all the 
Ostracionts which 1 have examined. The next question to be decided is the relation 
which the calcareous elements bear to these different sets of fibres. Whatever may 
be their modifications, it is only those fibres which, in the central and inferior laminae, 
are horizontal and parallel, that ever do become calcified. On exposing some of the 
vertical septa (18 d and 20 h) to the action of boiling Liquor Potassae, 1 got rid of the 
merely membranous portions, and preserved the calcareous elements intact. Fig. 27 
represents the lateral aspect of a fragment of a septum thus acted upon, which is 
obviously nothing more than a calcification of the interlaced fibres seen in fig. 24 d. 
It is a calcareous network with numerous lenticular meshes, 27 a, through which the 
flattened portions of the bundles of horizontal fibres have passed without calcifica- 
tion. The calcareous margin of each mesh is incised by a number of minute vertical 
fissures, 27 b. I have not been able to ascertain with certainty what function these 
fissures have fulfilled ; but I suspect that separate fibres raised from the surface of 
the common bundle have fitted into these small incisions, which would thus contri- 
bute in a very important manner to the fixation of the bundle in its place and increase 
the strength of the organism. 
The horizontal laminse (20 i) are perforated, and penetrated by the uncalcified ver- 
tical fibres, in precisely the same way. In the vertical section of the extreme marghi 
of one of these scales, fig. 22, we see that these horizontal bundles penetrate the 
lower portions of the uppermost calcareous layer. Thus they are seen passing- 
outwards at 22 d, whilst at e their transversely divided extremities are rendered 
visible, owing to the direction of the line of section, as explained at page 662. They 
do not ascend as high as the horizontal canals, 22 b. The laminae which enter into 
