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bone, one springing from the inner and the other from the 

 outer surface of the bony part of the spine. The channels 

 reach from the base of the spine, where it joins the operculum, 

 nearly to its point ; in the former situation, they are deep, and 

 the ridges of bone are separated to a comparatively wide dis- 

 tance, so as to form between them a capacious furrow for the 

 lodgment of a portion of the most bulky part of the gland, the 

 channel becoming gradually more and more shallow as it 

 approaches the point. Some idea probably may be formed of 

 the anatomical character of the spine by the accompanying 

 diagram, (plate 5, fig. 3 J which is intended to show the appear- 

 ance of a transverse section near its middle ; this section may be 

 made by using a sharp knife in the way of a saw, with a very 

 bght hand. 



Upon removing the whole of that portion of the operculum 

 to which the spine is attached, with the gland and integument 

 covering it, the situation of the gland may be observed even with 

 the naked eye, and appears hke a faint, whitish, transparent line, 

 running up each side of the spine, partly in and partly out of 

 the groove, (figs. 5 and 6.J The white appearance is much 

 broader at the base, where it is of a pyriform shape, becoming 

 more and more tapering until it reaches the point of the spine. 

 When the opercula have been steeped in spirit, the glands may 

 be seen under the integument forming distinct white bodies, 

 especially at the base. If the whole of these parts together be 

 subjected to a magnifying power of an inch focus, (and from 

 the partial opacity of the structures, the Lieberkuhn should be 

 then applied,) the glandular structure is still more perceptible; 

 at the base of the spine especially there is a part of the integu- 

 ment which is very free from pigment cells, and, being trans- 

 parent, it admits of the sacculated appearance of the gland being 

 seen conspicuously through it. 



When we wish to examine tne intimate structure of the 

 gland itself, the best plan is to take a portion of the operculum 

 with spine, &c, attached, and to fix it down by pressure with 



