Soles, turbots, and other flatfish are, as is well known, unsymmetrical.

They live and move on their sides, the under side being usually differently coloured from that which is kept uppermost.

Now the eyes of these fish are curiously distorted in order that both eyes may be on the upper side, where alone they would be of any use.

It was objected by Mr.Mivart that a sudden transformation of the eye from one side to the other was inconceivable, while, if the transit were gradual the first step could be of no use, since this would not remove the eye from the lower side.

But, as Mr.Darwin shows by reference to the researches of Malm and others, the young of these fish are quite symmetrical, and during their growth exhibit to us the whole process of change.