o4 INTRODUCTION. 



M. Geofiroy. Immediately under the skin, there 

 is a distinct and peculiar membrane composed of 

 rhomboidal cells, the walls of which are compressed 

 against each other as in young leaves. A longitu- 

 dinal aponeurotic band or raphe, proceeding from 

 the skin to the muscles, both on the back and 

 abdomen, divides it into two portions, one on 

 either side. The whole of its internal aspect is 

 doubled by a silvery aponeurosis, which is com- 

 posed of interlacing fibres. This tunic extends up- 

 wards as far as the eye, leaving a hollow space for 

 the pectoral fin, and downwards does not extend 

 below the ears; backwards it reaches no further than 

 the anal fin, and beyond that is simply aponeuro- 

 tic. The par vagum nerve runs under this aponeu- 

 rosis, and supplies it with numerous branches, 

 which penetrate it, to be distributed among the 

 cells. 



M. Geoffroy, as already stated, had previously 

 described this peculiar coat. To this M. Rudolphi 

 adds, that there is present, moreover, another re- 

 markable tunic, covered with minute cells, consist- 

 ing of a flaky irregular tissue, quite peculiar in its 

 nature. When a portion of this membrane is taken 

 hold of with a pair of pincers, its tissue appears to 

 be composed of loose tufts of exceedingly soft fibres, 

 without any regular arrangement, and without any 

 fatty matter in its composition. M. Valenciennes 

 describes the former of these tunics, M. Geoffroy's, 

 as a thick layer of spongy cellular tissue imme- 

 diately under the true skin, and strongly adhering 



