11. The original location of the eye is indicated in the adult by the direction first taken, as they leave the brain, by those cranial nerves having to do with the transposed eye.
12. The only well-marked asymmetry in the adult brain is due to the much larger size of the olfactory nerve and lobe of the ocular side.
13. There is a perfect chiasma.
14. The optic nerve of the migrating eye is always anterior to that of the other eye.
Fig. 130.—Larval Flounder, Pseudopleuronectes americanus. (After S. R. Williams.)
Fig. 131.—Larval Flounder, Pseudopleuronectes americanus. (After S. R. Williams.)
"The why of the peculiar metamorphosis of the Pleuronectidæ is an unsolved problem. The presence or absence of a swim-bladder can have nothing to do with the change of habit of the young flatfish, for P. americanus must lose its air-bladder before metamorphosis begins, since sections showed no evidence of it, whereas in Lophopsetta maculata, 'the windowpane flounder,' the air-sac can often be seen by the naked eye up to the time when the fish assumes the adult coloration, and long after it has assumed the adult form.