246 THE LIVING ANIMALS OF THE.WORLD 
their way by means of a horny projection on the lower jaw, and remaining buried at ebb-tide 
some § or 6 inches under the sand, when they are captured by fishermen, armed with rakes, for 
bait. When swimming in shoals, their presence is often betrayed by schools of porpoises, which 
feed greedily upon them, preventing their return to the bottom by getting under the shoal, 
whilst others swim round it. Mackerel also make large raids upon the ranks of such shoals. 
FLAT-FISHES may be reckoned among the most important of food-fishes, and besides are 
of quite peculiar interest, on account of the remarkable modifications of structure which they 
have undergone. They differ from all other vertibrates in that, save for the first few weeks 
of existence, they spend the whole of their lives with one side of the body uppermost — the 
right or left, according to the species. Whether resting or swimming, this position holds 
good. The newly hatched fish, however, maintains the normal poise of the body, the back 
being uppermost. Of the many changes which the organs of the body undergo during this 
strange transformation from a “round” to a “ flat” fish, one of the most interesting is that 
which concerns the eyes. These, in the very young fish, lie one on either side of the head; 
but as the fish grows older it begins to lie on its side on the ground, and ultimately, when 
it is two or three months old, loses the power of sustaining itself in an upright position 
altogether. The most remarkable feature in this very strange mode of development is, 
that as the ash comes to lie more and more on its side, so the eye which is undermost 
begins to move round to the other side, till eventually the two eyes lie side by side on the 
upper-surface. Strangely enough, in some species the eye moves round the head, passing 
over its edge, and so to its place beside the stationary eye, whilst in others it acquires its 
ultimate position by moving ¢kvough the head, sinking in on one side and appearing again on 
the other. The coloration of these fishes is also peculiar, in that the two sides are quite 
differently coloured, the upper side resembling in tone that of the sea-bottom, whilst the under 
side is pure white. In the young fish, before the habit of lying on one side has been 
acquired, both sides are coloured alike. The difference in coloration between the two sides of 
the adult fish appears to be due to the effect of light, since in flat-fishes kept in a tank with 
| 
Photo by W, Saville Kent, F.Z.S.} 
[ Milford-on-Sea 
HALIBUT 
The largest member of the Flat-fish Family, The back-fin usually commences much farther forward 
