LAMPREY. 449 



by a reference to the vignette ; the figure on the left hand of 

 which shows the flexible lip concealing the mouth ; the figure 

 on the right hand represents the rounded mouth, the small 

 and numerous tubercular teeth, and the central aperture lead- 

 ing by the throat to the stomach. 



The situation of the branchial cells, and the gills or 

 branchiae within these cells as they exist in the common River 

 Lamprey, or Lampern, as it is also called, are shown in the 

 right-hand figure at the bottom of page S^6 : and the water 

 obtains access and egress by seven small apertures on each 

 side of the neck, by the mouth of the fish, or by an aperture 

 through the upper part of the head which communicates with 

 the pharynx, and which communication is distinctly seen in 

 a divided head. 



The Lampreys, like the Sharks and Rays, have no swim- 

 ming-bladder ; and being also without pectoral fins, are usually 

 seen near the bottom. To save themselves from the constant 

 muscular exertion which is necessary to prevent them being 

 carried along by the current of the water, they attach them- 

 selves by the mouth to stones or rocks, and were in conse- 

 quence called PetromT/zon, or Stone-sucker ; while the circu- 

 lar form of the mouth induced the name of Cyclostomes, or 

 Round-mouthed Fishes, which was bestowed upon them by 

 M. Dumeril. 



In reference to the respiratory apparatus in the species of 

 this genus, Mr. Owen has remarked,* that " when the 

 Lamprey is firmly attached, as is commonly the case, to 

 foreign bodies by means of its suctorial mouth, it is obvious 

 that no water can pass by that aperture from the j^harynx to 

 the gills ; it is therefore alternately received and expelled by 



* Descriptive and Illustrated Catalogue of the Physiological Series of Com- 

 parative Anatomy contained in the Museum of the Royal College of Surgeons 

 in London, vol. ii. page 80. 



