174 FISHES CHAP. 



of the dorsal fin are detached from one another and greatly 

 elongated, and moreover extend along the middle of the dorsal 

 surface of the head. The first, which is the longest, terminates 

 in lobes or lappets of skin, and can be freely moved in every 

 direction by the muscles inserted into its base. By the agita- 

 tion of this lure or bait smaller Fishes, probably mistaking the 

 disturbance for the presence of a wriggling worm, are tempted to 

 their fate, and soon find themselves engulfed in the enormous 

 mouth of the artful angler.-' In some allied forms (e.g. Ceratias 

 Mspinosus and Oneirodes eschrichtii) ^ which live in the abyssal 

 darkness of the deep sea, use is made of the attraction which 

 light has to aquatic animals, and the fishing-rod spine termi- 

 nates in a phosphorescent organ, which is probably used for 

 enticing smaller. Fishes within the reach of the jaws of these 

 singularly modified Angler-Fishes.^ 



It is by no means improbable that examples of " warning " 

 coloration occur amongst Fishes. The brilliant colours of some 

 of the Trigger-Fishes (BaUstes, Monacanthus), Coffer - Fishes 

 (Ostracion), and Globe-Fishes (Tetrodon) are perhaps of this 

 nature. They are often associated with the presence of strong 

 spines, defensive and often erectile, either in connexion with the 

 dorsal fin or on the general surface of the body, and may therefore 

 serve the purpose of a danger signal to such predatory foes of 

 these Fishes as might otherwise be tempted to attack them — 

 to the mutual advantage of the Fishes themselves and their 

 would-be enemies. The British Weever-Fish (Trachinus) may 

 perhaps offer another example of warning coloration.* The Fish 

 is armed with poisonous spines on its opercula, and, in addition, 

 has a conspicuous black dorsal fin. When the body of the Fish 

 is buried in the sand, only its projecting dorsal fin remains to 

 indicate its whereabouts to predatory Gurnards, which might 

 otherwise mistake the Weever for harmless Fishes of similar 

 size and habits. The existence of " recognition " colours or 

 markings peculiar to the species, to enable individuals of the 

 same species to recognise one another and to keep together in 

 shoals, has not yet been proved. It is probable that the relatively 



^ For another view of the use of the "lure," see Cunningham, Marketable 

 British Marine Fishes, London, 1896, p. 3-38. 



^ Giiuther, Ohall. Reports, Zool. vol. xxii. 1887, p. 50. 



' Suggested by Liitken ; Giiuther, I. o. 



* Garstang, quoted by Poulton, op. cit. p. 165. 



