386 THE INFLUENCE OF LIVING SUEROUNDINGS. 



true corals, are conspicuous for their coloui'S. The surface of a 

 reef lying just under water has often been compared to a gay- 

 garden of flowers, and the splendour of such a ' bed ' of animals 

 is in fact quite astonishing. It is as though Mother Nature had 

 here given free play to the fancy she is elsewhere compelled to 

 restrain in some degree, by indulging her delight in lavishing all 

 the colours of the rainbow, and by inviting a motley company 

 of creatures to disport themselves among the flowers and fruit 

 of her submarine garden — blue and red star-fish, Holothurise of 

 every hue, and gaudily painted fishes. 



The fishes, in which the sexes are separate and which swim 

 about freely, may perhaps have preserved their brilliant colour- 

 ing by sexual selection, or even in the way put forward so 

 emphatically by "Wallace ; but neither hypothesis suffices as a 

 satisfactory explanation of the equa.lly bright colours of polypes. 

 No kind of sexual selection can here come into play, for the 

 simple reason that the sexes do not seek each other ; they are all 

 sessile animals, male and female ajike, and are obliged to throw 

 ofi" the sexual elements into the water and leave it to chance, or 

 rather to the currents, whether fertilisation is efiected or not. 

 Wallace's explanation is equally inapplicable. All polypes 

 are predatory creatures, feeding on fishes, crabs, worms, &c. ; 

 hence their striking and ornamental colouring would seem 

 rather to be a disadvantage to them, for, since they cannot move 

 about, they are fitted to catch such animals as approach too near 

 to them with their- long arms and the weapons with which these 

 are furnished ; and their colouring, therefore, would seem cal- 

 culated to warn all creatures swimming in the sea, even at a 

 distance, against coming within range of their perilous embrace. 

 This apparent disadvantage might perhaps be outweighed by a 

 greater advantage connected with this bright colouring, namely, 

 that it warns the fish that prey upon them not to approach — 

 which, of course, presupposes that those enemies have real 

 cause to dread the weapons of the polypes. This, however, is 

 by no means the case ; the fishes which feed on the true corals 

 — as the Scaridce among the Lahridce (Wrasses) and the Dio- 

 dontidce among the Plectognathi — are perfectly indifierent as to 

 whether the creatures they feed on try to clutch them with 



