Prof, lleid 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 in 

 the biconical cavities existing between each pair of vertebrse. 

 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- 

 tebrse, and filling 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 in 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 links. 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. 



