452 PETROMYZID/E. 



on each spawning place ; and while there employed, retain 

 themselves affixed by the mouth to a large stone." 



After the spawning season is over, the flesh of the Lam- 

 prey, like that of other fish, loses for a time its firmness 

 and other good qualities, and the weakened fish makes its 

 way back to the sea, to recruit its wasted condition. 



The food of the Lamprey consists generally of any soft 

 animal matter ; and in the sea it is known to attack other 

 fishes even of large size, by fastening upon them, and with 

 its numerous small rasp-like teeth eating away the soft parts 

 down to the bone. It is not very often caught while it 

 remains at sea. 



This species usually measures from twenty to twenty-eight 

 inches in length ; the head is rounded ; the form of the body 

 long and cylindrical, slightly compressed towards the tail ; 

 on the top of the head, rather before and between the eyes, 

 is an external aperture, which if examined with a blunt probe 

 is found to pass downward and backward, opening into a tube 

 on a line with the internal orifice of the first branchial sac : 

 along each outside of the neck are seven rounded apertures, 

 leading to as many branchial cells lined with a membrane 

 constructed like that of the gills in fishes ; each of these cells 

 has an internal opening into a tube which is closed by a car- 

 tilaginous pericardium at the bottom, but communicates up- 

 wards with the mouth : the lips surrounding the mouth, and 

 the numerous small teeth within, have been already referred 

 to : on the lower third portion of the body are two distinct 

 membranous dorsal fins, the second of which is the most 

 elevated, the edges of both convex ; a continuation of this 

 membrane round the extreme fleshy portion of the tail forms 

 a caudal fin, and a narrow slip passing upwards on the under 

 side forms an anal fin. 



The skin is perfectly smooth ; the colour of the body olive 



