70 



A HISTORY OF FISHES 



for the possession of an oval adhesive disc of complicated struc- 

 ture placed on the broad and flat upper surface of the head. 

 It is provided with a varying number of transverse plates with 

 free hinder edges, the whole being surrounded by a mem- 

 branous fringe (Fig. 30). By means of this disc the fish can 

 attach itself to any flat surface, a slight erection of the plates 

 creating a series of vacuum chambers. The adhesion is so 

 strong that a Remora can only be dislodged with difficulty, 

 unless it is pushed forward by a sliding movement. Some 

 naturaUsts state that when attached these fishes seem to become 

 quite insensitive, and show no sign of life however roughly 



^M^3 



Fig. 30. 



treated. Feeding as they do on other fish, the Remoras are 

 in the habit of attaching themselves to Sharks, Whales, Por- 

 poises, Turtles, and even occasionally to ships (cf. p. 427), and 

 in this way they are not only protected from their enemies, but 

 are carried without effort to fresh feeding grounds. Once 

 among a shoal of fish they soon detach themselves, dart oflT 

 and swim actively about in pursuit of prey, seeking a fresh 

 anchorage when their appetite has been satisfied. The point of 

 special interest about the sucker is that it is nothing more than 

 a very much modified spinous dorsal fin, whose rays have 

 become divided into two halves, bent outwards in opposite 

 directions, and have been transformed into the trans\erse 

 plates. The peculiar mode of life of the Remoras, and the 



