ON THE GENERAL MORPHOLOGY OF 'THE MYXINOID FISHES. On 
sections, the micro-anatomy of the connective tissues may be satisfactorily worked out 
in this way. 
Apart from the notochord, two kinds of skeletal tissue may be distinguished in 
Myxine—(a) cartilage and (b) pseudo-cartilage.* Further, there are at least two 
varieties of each kind, and all may be said to merge more or less perceptibly into each 
other. Of the cartilage, the two varieties are at once obvious. In the living condition, 
as already stated, the skeleton is uncoloured, but after it has been a long time in spirit 
a marked differentiation arises, the softer cartilage remaining white whilst the harder 
cartilage turns a deep reddish brown. This distinction is wonderfully emphasised by 
their staining reactions with methy]-blue-eosin, the soft cartilage staining blue and the 
hard red. There is also, of course, a considerable difference in consistency, as the 
terms soft and hard indicate. The combination of the morphological (already described) 
with the micro-chemical distinction makes the difference between typical hard and 
soft cartilage a very real one. The distribution of the two kinds of cartilage is 
illustrated in the figures by the two colours (representing the staining reactions with 
methyl-blue-eosin—soft cartilage, blue; hard cartilage, red), and hence there is no 
oceasion to refer to it further here. 
Hard Cartilage (fig. 3).—This consists of an intercellular substance or matrix in 
which very large cartilage corpuscles or cells are embedded. Each cell (ct. c.) is 
surrounded by a deeply staining thick capsule (c. ct. c.); but the matrix immediately 
around each capsule only stains slightly, and this, owing to the large size of the cells, 
accounts for the reticular appearance of the matrix emphasised by Pottarp, Wedged 
in between this secondary ground substance (s. g. s.), as it is called by ScHarrEr, is the 
staining portion of the matrix, or the cement substance (c. sb.), which more or less 
surrounds each ring of secondary ground substance. The cement is the most massive 
in older animals and in the larger cartilages. The cartilage cell itself consists of a very 
finely granular slightly staining reticulum, in which is embedded a round or oval 
nucleus (n. ct. c.) containing generally a single deeply staining nucleolar body 
surrounded by a clear space. In paraffin sections the nucleus appears clear and 
vesicular, with scattered globules of chromatin, whilst the sarcode is distinctly reticular 
and the centrosomes also visible. I have seen as many as four nuclei in one capsule, 
evidently prior to division, and the nucleolus itself may be multiplied. Various stages 
in the division of the cell, and the consequent formation of fresh intercellular substance, 
may be seen. With methyl-blue-eosin, the matrix stains red, the nucleus light blue, 
and the nucleolus a deep blue. 
Soft Cartilage.—This is the pro-cartilage of PaRKER and PoLLarp, but not the pro- 
cartilage of Srupnicka. It has a very strong affinity for methyl-blue, and in fact 
combines with this stain so intensely that it takes time to extract it. That there is, 
however, no genetic distinction between the hard and soft cartilage is shown by the fact 
* A term applied in 1878 to similar tissue in the frog by StapELMANN. I adopt it in preference to ScHAFFER’S 
more cumbrous “ vesicular supporting tissue.” 
TRANS. ROY. SOC. EDIN., VOL. XLI. PART III. (NO. 30). 112 
