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It would be excecdinsly interestino- to rear some of tliesc young 

 Turbots ill the aquarium, and it perhaps may be done if sufficient 

 food of a very small size could be given them, such as the roe of 

 small fish ; but it must be clearly understood that an aquarium 

 and a breeding pond have little or nothing in common. 



It has often struck me, when seeking for fish at the sea-side, 

 and still more when quietly examining them in the aquarium, 

 how very much the colour of these side-swimming flat fish assimi- 

 late to the sand or gravel on which they repose ; the Brill, for 

 instance, appears uniform and light-coloured when on sand, and 

 dappled when on pebbles. 



It appears that these fish can, apparently at will, change their 

 colours in response to their environment, and that they have the 

 power of contracting the dark colour into dapples or expanding it 

 over the body until, by suffusion, the upperside becomes of a 

 whity-brown. 



In a most interesting communication made, I am told, on this 

 subject to the British Association this year, it was shewn that by 

 dividing the nerves by which the animal communicates its will 

 to the muscles charged with the function of changing colour, the 

 pigment cells were no longer under the control of the fish, but 

 the colour remained in an accumulated patch in a certain space, 

 which was surrounded, or nearly so, with white. 



I have not had the pleasure of reading the paper, but shall be 

 curious to ascertain whether the small bony tubercles on the back 

 of the Brill, before adverted to, are points of attachment for 

 these muscles. 



The subject is a peculiarly interesting one, and the experiments 

 are precisely of that kind which an aquarium would give the best 

 facilities for. 



One thing, however, appears certain, that these bony tubercles 

 do not exist on the white or under side of the fish, unless it is 

 abnormally partially coloured. 



It must have struck every one that the size to which many 

 adult fish attain is indefinite ; quite unlike the higher vertebrates 

 in this respect, which generally attain an average size, varying 

 more or less in condition only. 



Now, speaking generally, this arises ft-om the law, that the size 

 of an animal is determined by the quantity of food it can obtain, 

 combined with the amount of exertion necessary to obtain it. 



Take the common Jack as an illustration. When the Jack is 



