aves the ovum, to the soles, which are entirely
thrown to one side."

Mr. Mivart has taken up this case, and remarks that a sudden spontaneous
transformation in the position of the eyes is hardly conceivable, in
which I quite agree with him. He then adds: "If the transit was gradual,
then how such transit of one eye a minute fraction of the journey
towards the other side of the head could benefit the individual
is, indeed, far from clear. It seems, even, that such an incipient
transformation must rather have been injurious." But he might have found
an answer to this objection in the excellent observations published
in 1867 by Malm. The Pleuronectidae, while very young and still
symmetrical, with their eyes standing on opposite sides of the head,
cannot long retain a vertical position, owing to the excessive depth of
their bodies, the small size of their lateral fins, and to their being
destitute of a swim-bladder. Hence, soon growing tired, they fall to
the bottom on one side. While thus at rest they often twist, as Malm
observed, the lower eye upward, to see above them; and they do this so
vigorously that the eye is pressed hard against the upper part of the
orbit. The forehead between the eyes consequently becomes, as could be
plainly seen, temporarily contracted in breadth. On one occasion Malm
saw a young fish raise and depress the lower eye through an angular
distance of about seventy degrees.

We should remember that the skull at this early age is cartilaginous and
flexible, so that it readily yields to muscular action. It is also known
with the higher animals, even after early youth, that the skull
yields and is altered in shape, if the skin or muscles be permanently
contracted through disease or some accident. With long-eared rabbits,
if one ear flops forward and downward, its weight drags forward all the
bones of the skull on the same side, of which I have given a figure.
Malm states that the newly-hatched young of perches, salmon, and several
other symmetrical fishes, have the habit of occasionally resting on
one side at the bottom; and he has observed that they often then
strain their lower eyes so as to look upward; and their skulls are thus
rendered rather crooked. These fishes, however, are soon able to hold
themselves in a vertical position, and no permanent effect is thus
produced. With the Pleuronectidae, on the other hand, the older they
grow the more habitually they rest on one side, owing to the inc