1 Ae te pal 
iat Me 
Prof. Reid on the Vogmarus Islandicus. 475 
of the hyaline and the cellular elements varied in the cartilaginous 
texture in these different situations, but in most of it the nucleated 
cells were very abundant. 
The surface of the transverse section of a vertebra (fig. 3) 
exhibits four different textures :—1. It is enveloped externally 
in a layer of dense areolar tissue, which also lines the interior of 
the cup-shaped cavities at the anterior and posterior ends of the 
vertebra. 2. The centre is occupied by a portion of the same 
gelatinous-looking substance which is seen in larger masses im 
the biconical cavities existing between each pair of vertebree. 
3. The walls of the narrow central canal containing this gelati- 
nous-looking substance consist of a peculiar, dense, flexible and 
strong structure which is prolonged outwards to the circumfe- 
rence in the form of rays (fig.3). 4. The intervals between these 
rays are filled up by a compact but much less resisting structure, 
which when torn up by the needles appears to be chiefly com- 
posed of very fine fibres mixed with granules. The gelatinous 
substance in the biconical cavities between the bodies of the ver- 
tebre, and filing up the narrow central canal in the body of each 
vertebra, is of the same intimate structure as the gelatinous sub- 
stance occupying a corresponding position im the spinal column 
of other fishes*. The texture which forms the rays as it proceeds 
outwards from the centre generally assumes the form of a waving 
band (fig. 4), which soon begins to bifurcate and reunite alter- 
nately at short intervals, presenting the appearance of a chain 
(fig. 4), the links of which, however; are frequently longer in the 
transverse than in the longitudinal direction. This chain with 
single links in its turn becomes a chain with double links (fig. 5), 
and when it reaches the circumference of the body of the ver- 
tebra its breadth has been increased by the addition of two or 
three more lmks. This appearance of a chain is caused by the 
transverse section of parallel tubes of a hexagonal and quadri- 
lateral shape (the former is the prevailing one) composed of this 
dense structure, and the links of the chain are the cut edges of the 
tubes. On making thin sections of the body of the vertebra in 
the longitudinal direction, a number of dark parallel lines may be 
observed (fig. 6 a) without any distinct indication of the presence 
of this tubular structure, and when a favourable slice has been 
procured, as represented in fig. 6, where the tubes have been cut 
across and a part of their course exhibited, the manner in which 
these dark lines are produced becomes apparent. The vertical 
walls (vertical in the position in which the portion under exami- 
nation is placed) of these quadrilateral and hexagonal tubes must 
be much thicker than the transverse, seeing that the empty spaces 
of the tubes are interposed between the latter, while the former 
* It is composed of large cells of irregular shape from lateral compression, 
having no distinct nuclei. 
