206 
begins to feed. It is probable that it feeds before the 
yolk has been entirely absorbed. The food is necessarily 
small, consisting of diatoms and larval molluses. It 
grows very slowly, and at the age of 25 days from hatching 
is only about 78mm. in total length and about 16mm. in 
height. After this the increase in height is relatively 
greater than that in length. Larval crustacea now form 
the principal food. The tail, which has hitherto preserved 
its embryonic homocercal character, now bends upwards 
at the tip, and ventral to this upturned portion fin rays 
begin to be formed (fig. 36). 
Up to 30 days after hatching the larva has retained 
its bilateral symmetry, and at this stage is precisely 
similar in form to the ordinary symmetrical Teleostean 
larva. The greater relative growth dorso-ventrally than 
longitudinally indicates the beginning of the metamor- 
phosis, and after the 30th day the left eye begins to move 
dorsally and anteriorly. 40 days after hatching it appears 
on the dorsal margin of the head just anterior to the right 
eye. On the 45th day the left eye has attained its defini- 
tive position on the apparent right side dorsal and anterior 
to the right eye. The larva is about 13}mm. long and 
65mm. high. During the period in which the eyes are 
rotating the young fish gradually acquires a new position 
in swimming; the vertical plane of its body slopes more 
and more from right to left as the eyes shift round so that 
in swimming the plane passing through both eyes is 
always horizontal. At the completion of metamorphosis 
the whole symmetry of the head has been profoundly dis- 
turbed, though that of the body remains as before, except 
that the opening of the ureter has shifted from the median 
ventral line to the right side. The horizontal swimming 
plane of the whole body has been rotated through a right- 
angle and the fish rests and swims on its morphological 
