8 TENERIFE. 



were obtained with the two sharks. They were seen to shift 

 their position on the sharks frequently as these struggled in 

 the water fast hooked. 



The Remora is a fish provided, as a means of attachment, 

 with an oval sucker divided into a series of vacuum chambers 

 by transverse pleats. The sucker is placed on the back of the 

 fish's head. l"he animal thus constantly applies to the surfaces 

 to which it attaches itself, such as the shark's skin, its back. 

 Hence the back being always less exposed to light is light- 

 coloured, whereas the belly, which is constantly outermost and 

 exposed, is of a dark chocolate colour. The familiar distribu- 

 tion of colour existing in most other fish is thus reversed. No 

 doubt the object of the arrangement is to render the fish less 

 conspicuous on the brown back of the shark. Were its belly 

 light-coloured as usual, the adherent fish would be visible 

 from a great distance against the dark background. The result 

 is that when the fish is seen alive it is difificult to persuade 

 oneself at first that the sucker is not on the animal's belly, and 

 that the dark exposed surface is not its back. The form of 

 the fish, which has the back flattened and the belly raised and 

 rounded, strengthens the illusion. When the fish is preserved 

 in spirits the colour becomes of a uniform chocolate, and this 

 curious effect is lost. When one of these fish, a foot in length, 

 has its wet sucker applied to a table and is allowed time to lay 

 hold, it adheres so tightly that it is impossible to pull it off by 

 a fair vertical strain. 



Fishing for sharks was a constant sport on board the ship 

 when a halt was made to dredge anywhere within a hundred 

 miles or so of land in the tropics. Sharks were not met with 

 in mid-ocean. Mr. Murray* examined these sharks thus 

 caught, and reports that they all, whether obtained in the 

 Atlantic or Pacific Ocean, belonged to one widely distributed 

 species, excepting one other kind obtained off the coasts of 

 Japan. The hammer-headed shark {Zj'gc^na malleus) was 

 taken by us only with a net on the coasts. 



The sharks were often seen attended by one or more Pilot- 

 fish {Naiicnites sp.), as well as bearing the "Suckers " attached 

 to them. I often watched with astonishment from the deck 

 this curious association of three so widely different fish, as it 

 glided round the ship like a single compound organism. 



The sharks, as a rule^ were not by any means so easily 

 caught as I had expected. Frequently they were shy and 

 would not take a bait near the ship, though they never failed 

 tf) bite if it was floated some distance astern by means of a 

 wooden float. It is always worth while for naturalists to take 

 * J. Murray, "Prop. R. Soc.," No. 17G, 1876, p. 540. 



