112 MARVELS OF FISH LIFE 
acquiring the appearance of the adult, now enters upon 
the stage of adolescence. 
This change from the transparent post-larval stage 
to that in which the fish assumes the shape and silvery 
appearance of the adult, does not call for our special 
attention among round fishes, such as the cod, the 
haddock, and the mackerel. Among flat fish, however, 
such as the plaice, the sole and the turbot, a remark- 
able transformation occurs during the post-larval 
stage. 
Flat-fish larvee begin by swimming near the surface 
in an upright position like the larvee of other fishes. 
Next, they flatten from side to side, and gradually 
approach the bottom, to end up by lying on their right 
or left sides, as the case may be. 
If no alteration occurred in the position of the eyes 
when the young fish had settled on the bottom, one eye 
would be buried in the sand. To prevent this during 
the transformation of the larval flat fish, the cranium 
in the region of the orbit rotates on its longitudinal axis 
until the two eyes lie in a vertical plane, the eye from 
the underside being above the other. Not infrequently 
it is stated that the eye from the underside travels 
round the head, but this is incorrect for, as explained, 
it is the cranium that rotates, and the relative position 
of the eyes does not alter. 
Plaice, soles, flounders, dabs, lemon soles and halibut, 
after they have flattened, all lic on their left side, while 
turbot and brill lie on their right side. 
