108 CAN FLAT-FISH CHANGE COLOUR AT WILL? [PARTI 
additional light on the subject from his own ex- 
perience, and I hesitate to express an opinion at 
variance with that of so accurate an observer of 
nature. I cannot however but fancy that in this 
instance he may have been deceived by appear- 
ances. Undoubtedly the Flat-fish does apparently 
assume the colour of the bottom on which he rests, 
but, so far as my observation’ extends, this is only 
because, the moment that he halts, by a motion of 
his fins and tail so rapid as to be almost imper- 
ceptible, he throws up over his back some of the 
surrounding sand, working himself down as he 
does it to a lower level. He thus becomes in a 
wonderfully short space of time almost invisible 
to an unpractised eye, and might easily be sup- 
posed actually to have changed colour. 
I do not, of course, go the length of saying 
that Flat-fish do not 7m time become assimilated 
in colour to that of the bottom on which they 
generally lie. On the contrary, knowing that 
other fish—Trout for instance—do so, a fact which 
cannot but have forced itself on the notice of every 
angler, I should have been much surprised had 
T found that this property was not participated in 
by Flat-fish. My observations merely extend to 
their supposed power of changing colour aé will. 
