The Cyclostomes, or Lampreys 491 



land-locked and reduced in size by living in rivers only. Such 

 land-locked marine lampreys (Petromyzon marinus unico'.or) breed 

 in Cayuga Lake and other lakes in New York. The marine forms 

 reach a length of three feet. Smaller lampreys of other genera 

 six inches to eighteen inches in length remain all their lives in 

 the rivers, ascending the little brooks in the spring, clinging to 

 stones and clods of earth till their eggs are deposited. These 

 are found throughout northern Europe, northern Asia, and 

 the colder parts of North America, belonging to the genera 

 Lampelra and Ichthyomyzon. Other and more aberrant genera 

 from Chile and Australia are Geotria and Mordacia, the latter 

 forming a distinct family, Mordaciidoz. In Geotria, a large and 

 peculiar gular pouch is developed at the throat. In Macroph- 

 thalmia chilensis from Chile the eyes are large and conspicuous. 

 Food of Lampreys. The lampreys feed on the blood and flesh 

 of fishes. They attach themselves to the sides of the various 

 species, rasp off the flesh with their teeth, sucking the blood 

 till the fish weakens and dies. Preparations made by students 

 of Professor Jacob Reighard in the University of Michigan show 

 clearly that the lamprey stomach contains muscular tissue as well 

 as the bidod of fishes. The river species do a great deal of mis- 



FIG. 292. Lamprey, Petromyzon marinus L. Wood's Hole, Mass. 



chief, a fact which has been the subject of a valuable investiga- 

 tion by Professor H. A. Surface, who has also considered the 

 methods available for their destruction. The flesh of the lam- 

 prey is wholesome, and the larger species, especially the great 

 sea lamprey of the Atlantic, Petromyzon marinus, are valued as 

 food. The small species, according to Prof. Gage, never feed on 

 fishes. 



Metamorphosis of Lampreys. All lampreys, so far as known, 

 pass through a distinct metamorphosis. The young, known as 

 the Ammoccetes form, are slender, eyeless, and with the mouth 



