246 A HISTORY OF FISHES 



When the host is feeding on some other animal the Rcmora 

 obtains some of the fragments floating in the water, but on 

 some occasions the Shark is used merely as a vehicle to carry 

 the Remora to fresh feeding-grounds, where it detaches itself 

 and becomes an independent hunter. Often, however, the 

 Remora enters the mouths or gill-cavities of large Bony Fishes 

 such as the Sword-fish (Xiphias), Sail-fish (Istiophorus) , and 

 Sun-fish (Mold); it appears to be tolerated by its host, and 

 gains not only protection from enemies, but also scraps of 

 food. 



Interesting examples of commensalism occur among the 

 Pomacentrids or Damsel-fishes (Pomacentridae) of tropical coral 

 reefs, some of which are in the habit of entering into partnership 

 with sea anemones. In many cases the fish seems to be an 

 uninvited guest, conferring no benefit on the tolerant host, 

 but Mr. Saville Kent has described an association of this nature 

 in which it is claimed that both parties to the partnership 

 derive a benefit. Among the coral reefs of Thursday Island in 

 the Torres Straits between New Guinea and Australia, he 

 found a brilliantly coloured Pomacentrid (Amphiprion) , bright 

 vermilion red with three white cross-bands, which habitually 

 lives in the interior of an anemone measuring no less than two 

 feet in diameter when fully expanded. The fish seems to be 

 quite unharmed by the veritable battery of paralysing stinging- 

 cells with which the tentacles of the anemone are armed, or 

 by its digestive juices. In the ordinary way the slightest touch 

 of any animal is sufficient to cause the anemone to contract 

 and to seize the intruder in its tentacles, and it is open to 

 question whether it really tolerates the presence of the fish or 

 whether the latter is active or skilful enough to avoid contact 

 with the tentacles or with the walls of the gastric cavity. 

 Mr. Kent is convinced that the brilliantly coloured fish serves 

 the anemone as a decoy to the mutual benefit of itself and of 

 its host. Issuing forth, it attracts the attention of some watchful 

 predaceous fish, and when chased plunges back into the interior 

 of the anemone: this brings the pursuer within reach of the 

 tentacles with their deadly stinging-cells ; it is promptly paralysed 

 and engulfed, and anemone and its assistant share the spoils ! 



Among the members of the tribe of Rudder-fishes [Stroma- 

 teidae) the young individuals often shelter under jelly-fishes, 

 apparently without fear of the long tentacles with their myriads 

 of poison-cells. One of these fishes is called the Portuguese 

 Man-of-war-fish {Nomeus) on account of its constant association 



