174 GIANT FISHES 



or Sucking-fish (Echeneis naucrates), and the Common Remora 

 (Remora remora). Both these fishes have an almost cosmo- 

 politan distribution in warm seas, and the latter is an occasional 

 visitor to the British Isles. 



These remarkable fishes can scarcely be said to merit the 

 description of giants, and their inclusion in this book must 

 be justified by the fact that they are so universally associated 

 with the larger oceanic fishes, and are so often seen by ocean 

 voyagers. 



Their most interesting structural peculiarity is, of course, 

 the adhesive disc on the head. By means of this apparatus a 

 Remora is able to attach itself to any flat surface, a slight 

 raising of the transverse plates, or laminae, creating a series of 

 vacuum chambers. The adhesion is very strong, and to 

 dislodge a fish from any object to which it is clinging it is 

 necessary to pull it forwards, thus lowering the plates ; a 

 backward pull only serves to raise the plates, and the harder 

 the pull the firmer becomes the attachment. The interest 

 of the sucking disc to the scientific man lies in the remarkable 

 fact that it is in reality nothing more or less than the very 

 much modified spinous dorsal fin, the spines of which have 

 become divided into halves, bent outwards in opposite 

 directions, and transformed into the transverse plates. It is 

 of some interest to note that a fossil Remora, remains of which 

 have been found in rocks of the Eocene period, had a much 

 narrower sucking disc, which was placed behind the head, 

 and both in form and position this was more like a norma) 

 dorsal fin than that of its descendants living to-day. 



Dr. Regan has pointed out that the broader gill-covers and 

 the forked tail of this extinct fish indicate that it was a 

 stronger swimmer than the existing Remoras, and it seems 

 likely that it swam more and held on less than they do. " In 

 form it was not unlike a pilot-fish," he writes, " and it is 

 evident that the sucker-fishes must have been derived from 

 fishes which had, as the pilot-fish has to-day, the habit of 

 associating with sharks. The spinous dorsal fin of the pilot- 

 fish and of other oceanic fishes of the same type, with the 

 spines folded back within a groove, might possibly have some 

 power of adhesion if the edges of the groove were applied to 

 another object and the spines were then slightly raised." 



