238 



AMERICAN FISHES. 



shark in the water below, shining all over with phosphorescence. Now 

 this phosphorescence is considered by most naturalists to be due to the 

 presence of animalcules, and if so, it may reasonably be presumed that the 

 pilot-fishes live on these animalcules, for they are frequently seen clinging 

 to the sides of the shark." 



The Pilot-fish does not always leave the vessels on their approach to 

 land. In summer, when the temperature of the sea-water is several 

 degrees above the average, Pilots will follow ships to the south coast of 

 England into the harbor, where they are generally speedily caught. 

 Pilot-fish attain a length of twelve inches only. When very young their 

 appearance differs so much from the mature fish that they have been 

 described as a distinct genus, Naiiclcnis. This fry is exceedingly common 

 in the open ocean, and constantly obtained in the tow-net: therefore the 

 Pilot-fish retains its pelagic habits also during the spawning season, and 

 some of the spawn found by voyagers floating on the surface is, without 

 doubt, derived from this species.* 



The Pilot-fish has been observed in one or two instances about New 

 York, and also has been recorded from South Carolina. It is, however, 

 rare in the Western Atlantic, and our museums have very itw specimens. 



*Gunther : Study of Fishes, p. 414. 



