758 MR FRANK J. COLE 
that the soft cartilage, where it is connected with the hard—as, for example, the lateral 
labial cartilage with the external bar of the anterior segment of the basal plate—always 
passes imperceptibly into the hard cartilage without any demarcation or trace of suture. 
Hence we may regard the hard and soft cartilages as modifications of the same ancestral 
tissue. On the other hand the soft cartilage, for example, of the caudal fin and of the 
branchial skeleton undoubtedly approaches rather the structure of the hard pseudo- 
cartilage, thus connecting up the two kinds.* The essential difference between typical 
examples of the two varieties of the cartilage lies in the great reduction of the matrix, 
and of its character, in the soft cartilage. This in some places is a continuous, homo- 
geneous, almost fibrous looking network; but, generally, cell capsules may be clearly 
distinguished, and secondary ground substance may even be added. Apart from this, 
the intercellular network is distinctly comparable to the cement substance of the hard 
cartilage, and is its characteristic feature. The cells and nuclei of the soft cartilage differ 
in no essential respect from those of the hard cartilage. 
Pseudo-Cartilage (fig. 4)—The structure of the hard pseudo-cartilage, for we 
may distinguish hard and soft varieties here also, is best seen in the posterior segment 
of the basal plate and in the superior chondroidal bar. If a thin, free-hand, transverse 
section is made of the former it is seen to be U-shaped, and enclosed by a thick 
perichondrium of stout. connective tissue fibres among which are interspersed groups 
of nuclei. Both the dorsal concave and the ventral convex borders are lined by a 
single palisade of vertical chambers, those at the latter border being much the larger. 
The central portion of the cartilage is ocenpied by similar chambers (but of much 
smaller size and irregular shape), and also by stout fibrous septa which usually pass 
more or less directly from one border to the other, branching as they go. All the 
peripheral chambers and many of the central ones are further divided by exceedingly 
fine partitions into a number of loculi, each loculus containing one cell formed of a 
glassy, transparent, unstaining sarcode, and one or more peculiar coarsely granular nuclei. 
These nuclei usually have one or more nucleolar bodies, each surrounded by a clear 
area. In some of the loculi a number of nuclei, each with an obvious nucleolus, were 
massed together, whilst the occurrence of centrosomes in these cells has been already 
mentioned. In the central loculi, the nuclei are generally much larger and of a very 
irregular shape. .In spite of the fact that the matrix is here almost absent and its 
place taken by fibrous septa, and that the character of the cells is different, we may 
directly compare the pseudo-cartilage with the true cartilage in terms of the soft 
cartilage of the caudal fin and branchial skeleton. AyrERS and Jackson state’ that the 
pseudo-cartilage of the posterior seement of the basal plate resembles rather the structure 
of the notochord than the cartilage of the remainder of the skeleton ; but this certainly 
cannot be accepted. 
The soft pseudo-cartilage may be best studied by sections of the thick pad at the 
cephalic end of the basal plate (figs. 1 and 10). It has essentially the same structure 
* (Op. the description of these two cartilages, and especially of the superior chondroidal bar. 
