INSTINCTS AND EMOTIONS IN FISH. 51 



and caused its rapid flight. Many species are gregarious, moving 

 about in large schools ; others, again, merely in pairs. 



During the breeding-season most, if not all, Teleostean fishes 

 have more resplendent tints than at any other period of the year, 

 and •which may be for the purpose of mutual attraction. A good 

 example is seen in the Salmon, while I have observed the same 

 circumstance occur in the beautiful little Groby (Periophthalmus 

 Schlosseri) which frequents the river Irrawaddi and its banks. 

 Jordan and Copeland*, observing upon the John Darters (Etheo- 

 stoma blennoides), remark upon a male in their aquarium which 

 underwent, almost in an instant, an entire change of pattern (in 

 the colours of his body) upon the introduction of a female fish of 

 the same species. Even after two weeks the novelty had not 

 worn off, though his body-colours varied much from hour to hour, 

 but had not reverted to his original dress. 



There is a curious instinct of some fishes to take up their resi- 

 dence inside other animals, or else to attach themselves to them 

 in order to profit by the greater power of locomotion in their 

 host, from whose body, however, they draw no sustenance, but 

 merely partake of such food as comes within their reach. These 

 latter, termed Commensals^ by Van Beneden, may be either free 

 or fixed to their host ; and a common example of a Commensal is 

 the Sucking-fish (Echeneis), which, having but weak fins, attaches 

 itself to any large swimming or floating object, animate or inani- 

 mate, as ships, sharks, whales, &c, not for the purpose of feeding 

 upon them, but to enable it to profit by their powers of locomo- 

 tion, and so enable it to capture other small fishes, upon which it 

 mostly subsists. Commerson assures us that, having applied his 

 thumb to the adhesive organ of a living Sucking-fish, the adhesion 

 was so strong that it became numbed, and an almost partial para- 

 lysis continued for some considerable time subsequently. During 

 stormy weather it adheres like limpets to a rock. Another cir- 

 cumstance related by Commerson is, that in the Indian seas a ring 

 is fastened round the tail of one of these fish so as to prevent its 

 escape ; to the ring is attached a long cord, and it is thus carried 

 in a vessel of salt water ; and when boatmen observe a turtle 

 asleep on the surface of the water, they approach as close as they 

 can, then throw the Sucking-fish into the sea : it attaches itself 

 to the breast of the turtle, and is thus drawn into the boat. The 



* American Journal, 1878, p. 338. 



t Bulletin Ac. Belg. 1869, xxviii. p. 621. 



