294 NATURAL HISTORY. 



and even in the same specimen the numbers may differ on opposite sides 

 of the body. 



The lampreys derive their common name from the Latin word lampetra, 

 which means 'stone-sucker, an allusion to the habit these animals have of 

 attaching themselves to stones, for which their sucking-mouth is well 

 adapted. It is not to stones alone that they attach themselves, for their 

 normal manner of life is to adhere to fishes. Then the sharp teeth rasp 

 and abrade the skin, and the blood which flows from the wound forms 

 their food. The hag-fish goes a step farther in this parasitic life ; for it 

 carries the gnawing so far that it makes a hole into the body cavity of the 

 fish, and then it enters and lives there an internal parasite until its 

 host dies. 



Every spring the lampreys ascend the streams in large numbers, seek- 

 ing a place to lay their eggs. These migrations are mostly made at night, 

 and at the time of the run the people in certain localities catch large quan- 

 tities of them for food, while in other places they are entirely neglected. 

 Those that escape deposit their eggs, and then die. 



