166 



into one mass, at others having a granular appearance ; the 

 other cells are smaller and occupy the interstices between the 

 large ones. (Vide fig. 7. J 



When we come to examine the stinging apparatus of the 

 dorsal fin, we find that each spine comprising it, consists, like 

 the opercular ones, of two grooves, in each of which a gland 

 is partly lodged, the spines and glands being covered in by the 

 integument, as in the other case. The grooves are similar in 

 principle, though not in appearance, to those of the oper- 

 culum ; instead of being formed of two equal ridges of bony 

 matter springing from the sides of the spine, a transverse 

 section reveals a shape which is shown in the diagram, the 

 broad part-^ being placed posteriorly, and the prominence^) 

 anteriorly; in this way the two grooves gg are formed, so 

 that the glands are placed upon the anterior part of the spines, 

 separated from each other by the bony prominence before re- 

 ferred to. The channels are not so deep and well developed as 

 in the opercular spines, neither are the glands so large ; in- 

 stead of being expanded at the base bke those of the oper- 

 culum, they are more of a linear shape. After being steeped 

 in spirit these glands become white, hard and friable, and may 

 be pushed out of their grooves, with the point of a needle, 

 from base to point, they then have some resemblance to a 

 small thin grub or worm ; at other times they come out of the 

 grooves and appear bke two little white streaks upon the inner 

 surface of the integument which forms the sheath of the spine. 

 The dorsal glands are not perceptible to the naked eye either 

 before or after immersion in spirit, as the integument which 

 covers them in is much thicker, aud the membrane is 

 charged with a much greater quantity of pigmentary matter 

 than in the case of the operculum, besides which they are not 

 above a third part of the size. It is more difficult to examine 

 the dorsal than the opercular glands, first because they are 

 much smaller, secondly because the thickness and blackness 

 of the integument completely obscures them from vision by 



