242 THE SENSE-ORGANS AND PERCEPTION OF FISHES. 



Flounder (P. flesus) . 



Shorter pipe-fish {Nerophis 



cequoreus) . 

 Worm pipe-fish {N. lumhrici- 



formis) . 



Turbot {Rhomhus maximus) . 

 Brill [Rhomhus levis). 

 Miiller's topknot {Zeugopterus 



punctatus) . 

 Plaice (Pleuronectes plafessa) , 

 Dab (P. limanda). 



Sight. — The sense of sight in these fishes is developed in various 

 degrees. In some^ as in the bream [Pagellus], the eyes are practi- 

 cally fixed ; while in others, as in the pipe-fishes {Syngnathidw) , dory 

 (^Zeus faher), and wrasses [Labridm), the eyes are capable of consider- 

 able movement, and are used independently like those of the chame- 

 leon. None of the fishes observed appear to distinguish food (worms) 

 at a greater horizontal distance than about four feet, and for most 

 of them the vertical limit seemed to be about three feet ; but the 

 plaice at the bottom of the tank perceived worms when at the 

 surface of the water, being about five feet above them. Though the 

 distance of clear vision seems to be so small for objects in the water, 

 many of these fish (plaice, mullet, bream) notice a man appearing on 

 the other side of the room, distant about fifteen feet from the window 

 of the tank. When hungry they swim up to the side of the tank and 

 show great excitement if a person approaches. The same may be seen 

 in the case of Octopus at Brighton, which, when the crowd collects 

 in front of the tank, by its rapid and excited movements shows that 

 it recognises the signs of approaching feeding-time.* The range 

 of sight of fishes on the whole appears to be short. The sight of 

 the wrasses {Labridx) in particular is plainly adapted for vision at 

 very close quarters ; for the habit of these fishes is to search for their 

 food by minute examination of the bottom, weeds, &c., after the 

 manner of insectivorous birds. 



None of the fish seem to get any lasting appreciation of the 

 nature of the plate-glass wall of the tank. The same fish will again 

 and again knock its head against the glass in trying to seize objects 



* In this case there is some doubt as to whether the Octopus does not recognise feeding- 

 time by the help of its internal sensations. I have as yet had no opportunity for accurate 

 experiment; but Mr. Wells tells me that both the Octopus and conger begin to swim 

 about at feediug-time, whether any one is at the top of the tank or not. The conger are 

 fed on alternate days, and Mr. Wells assures me that they distinguish these days, and do 

 not get excited on the off days. On two occasions only I have watched them myself. The 

 first was not a feeding-day, and they were not swimming about; but they certainly were 

 actively moving to and fro on the second visit, which was one of their feeding-days, as 

 also were the eels, which is still more surprising in view of their exceedingly nocturnal 

 habits. So far, therefore, as my observation went, it quite bore out the statement of the 

 superintendent. The fishes at Plymouth have not hitherto been fed with regularity, as 

 their meals have to be arranged with a view to other experiments, so that no conclusions 

 on this point can be drawn from them, 



