616 PETROMYZID.E. 



aperture, forms in addition a caudal and an anal fin, which 

 no doubt materially assist this fish in swimming. In colour 

 the Myxine is dark brown along the back, lighter chestnut 

 brown on the sides, and yellowish Avhite underneath. 



The vignette here added is from a drawing by Mr. Clift, 

 engraved for the Philosophical Transactions for the year 

 1815, where it illustrates a paper by Sir E. Home on the 

 organs of respiration in the Lamprey and Myxine. 



The upper angle of the figure exhibits the single spiracle, 

 about it the eight tentacula, on the centre of the palate the 

 single hooked tooth ; to the right and left are the double 

 rows of lingual teeth : an inch below, on each side, are the 

 six branchial cells, with their internal communications Avith 

 the central canal ; on the outside each cell communicates with 

 a tube that is common to the six cells on that side, which, 

 passing downward, ends at the external aperture below. 

 Beneath this is the stomach and intestinal canal, which, as 

 in the Lamprey, is straight ; the rounded marks along the 

 margin on both sides from end to end show the numerous 

 mucous glands that have already been referred to. It is 

 impossible to dissect a Myxine, and attend to the structure 

 and substance of its investing skin, without being forcibly 

 reminded of its great resemblance to the investing mantle of 

 the Cephalopods. 



The relations of structure in the Myxine to the Lampreys 

 on the one hand, and the first class of mollusca, the Cepha- 

 lopods, on the other, appear to prove that the situation 

 claimed for this fish by Bloch, and systematic authors since 

 his time, is the natural one. The relation to the Lampreys 

 is shown in the elongated, cylindrical form of the body ; the 

 single spiracle on the head ; the general similarity in the 

 parts of the mouth ; the character of the branchial cells, and 

 the viscera. 



The relation to the Cephalopods i.s apparent in the eight 



