272 ^Ir. E. W. Giidger on the 



The earliest references to this interesting fish are to be 

 fouiul in Aristotle's 'History of Animals/ A fish having 

 such an extraordinary structure as the suelving-disk and 

 liaving such unusual habits could hardly be expected to 

 have escaped the keen observation of the Father of Natural 

 History. Yet there is nothing in Aristotle's writings 

 to indicate that he ever saw or at any rate that he ever 

 examined the Echeneis with the care which he bestowed on 

 the other animals of which he wrote. In Prof, D'Arey 

 AY. Tliompson's scholarly translation (Oxford, 1910), one 

 may read (Rook II. 14, '505 b, 19-22) : " Of fishes whose 

 habitat is in the vicinity of rocks there is a tiny one, which 

 some call the Echeneis or ' ship-holder ' . . . . Some people 

 assert that it has feet, but this is not the case : it appears, 

 however, to be furnished with feet from the fact that its 

 fins resemble these organs." Again (Book V, 31, 557 «, 

 30-31): "In the seas between Gyrene and Egypt there 

 is a fish that attends on the dol})hin which is called the 

 ' dolphin's louse.' This fish gets exceedingly fat from 

 enjoying an abundance of food while the dolphin is out in 

 pursuit of its prey." 



In a footnote^ Prof. Thompson identifies this fish as 

 Naucrates diictor, a pilot-fish fouTid in the Mediterranean. 

 Now the term pilot-fish is applied rather indefinitely to a 

 number of different fishes. The Echeneis or Reniora is 

 possibly the one best known, from its habit of sticking to 

 dolphins, sharks, or any large fishes and swimming before 

 their snouts. In our waters Seriola zonula and S. carolinensis, 

 amber-fishes of the family Carangidse, are found associated 

 with sharks and are called pilot-fishes. They are likewise 

 found around the rudders of vessels and hence are also called 

 rudder-fishes. The Naucrates dudor of Prof. Thompson 

 is a pilot-fish of the same family but of a different genus. 

 It is found in warm waters throughout the world and has 

 the same habits as the other pilot-fishes. 



Thompson's footnote thus leads one away from the idea 

 that the "dolphin's louse." is a sucking-fish, but it should 

 be noted that this last reference comes in a section devoted 

 to sucking insect parasites, lice, ticks, and fleas, and con- 

 chules with those crustaceans, '' sea-lice " so called, which 

 live parasitically on fishes. So from this internal evidence 

 it seems probable that the fish referred to is an Echeneid, a 

 sucking-fish, which attaches itself in a louse fashion to the 

 dolphin as these fish are known to do *. 



* In a short note published in ' Science ' for September 1, 1916, the 

 present writer endeavoured to show that Prof. Thompson's identification 



