The Sea Lamprey. 413 



the present instance of the Mursena this resemblance, as re- 

 garded the shape, was thought sufficiently close to warrant 

 the transfer, with some little qualification, of the name of one 

 of these fishes to the other. Rondeletius is sufficient authority 

 for saying, that the sea lamprey was sometimes called Muraana 

 simply, or Murcena jiuviatilis, the River Mursena, which he 

 distinguishes by an anatomical difference in the head from the 

 Mura3na of the sea ; and he thinks the comparison of one with 

 the other not amiss. There is much probability also in the 

 opinion that it is the lamprey which is mentioned by Ausonius, 

 under the name of Mustellax, although Cuvier has said that the 

 Burbolt is the species intended by this Roman poet. The im- 

 portant fact, however, of its migrating habit from salt water, 

 which he refers to, and which is not a character of the Burbolt, 

 and the description of its colour, appear sufficient to decide the 

 question : — 



" All through, the ponds of Tster's double name, 

 Frothing the surface, the Mustella came ; 

 Watched by observant eyes it holds its way, 

 And safely shelters in our favoured bay ; 

 Bringing new riches to the wide Moselle ; 

 And its bright beauties who can paint or tell ? 

 On breadth of heavenly blue are dots of black, 

 Each circled yellow through the luscious track 

 Along the slippery surface of its back. 

 Prom head to vent it suits the nicest taste, 

 But all behind is dry, and thrown to waste." 



Attsonius' s Moselle. 



The fact that the Burbolt is still called Motella in some 

 parts of France will weigh but little when we call to mind how 

 common it is for different sorts of fishes to bear the same name, 

 as also that the same fish is known by several names in different 

 parts of the same country. 



This species of lamprey is often taken in the sea, but always 

 under peculiar circumstances, which have reference to remark- 

 able instinctive habits ; and these, again, are worthy of notice 

 as offering explanation of the use of the curious structure of its 

 mouth, and of the organization which serves it for the purpose 

 of breathing. This remarkable structure we shall by and by 

 describe, but at present it is sufficient to say, that the mouth, 

 when open, forms an expanded disk, round the deepest portion 

 of which there is an arrangement of rasping teeth ; and these 

 the fish has the power, however difficult it may appear, of 

 bringing into contact with any surface on which it chooses to 

 lay hold. By an exhausting action through which the air and 

 water are removed, a vacuum is produced ; and thus the fish 

 becomes fixed without any further exercise of muscular action. 

 The bottom of a ship or boat is frequently the object to which 

 it attaches itself, and it becomes a question what is the inten- 



