PROGRESS OF MICROSCOPICAL SCIENCE. 15F 
has its eyes in the ordinary position, comes to have both organs at the 
same side of the body :—*“I captured one day a number of flounders 
(about an inch in length) closely allied to the Plagusiz of Steenstrup, 
the so-called Bascania of Schiédte ; they were so perfectly transparent 
that they seemed the merest film on the bottom of the glass vessel in 
which they were kept. They were still entirely symmetrical, the 
eyes well removed from the snout, with a dorsal fin extending almost 
to the nostril, far in advance of the anterior edge of the orbits of the 
eyes. They were of course at once set down (from their size) as be- 
longing to a species of flounder in which the eyes probably remained 
always symmetrical, and I prepared to watch its future development. 
It was therefore with considerable interest that I noticed, after a few 
days, that one eye, the right, moved its place somewhat towards the 
upper part of the body, so that when the young fish was laid on its 
side, the upper-_half of the right eye could be plainly seen, through 
the perfectly transparent body, to project above the left eye. The 
right eye (as is the case with the eyes of all flounders), being capable 
of very extensive vertical movements, through an arc of nearly 180°, 
could thus readily turn to look through the body, above the left eye, 
and see what was passing on the left side, the right eye being of 
course useless on its own side as long as the fish lay on its side. I 
may mention here that this young flounder, until long after the right 
eye came out on the left side, continued frequently to swim vertically, 
and that for a considerable length of time. This slight upward 
tendency of the right eye was continued in connection with a motion 
of translation towards the anterior part of the head till the eye, when 
seen through the body from the left side, was entirely clear of the left 
eye, and was thus placed somewhat in advance and above it, but still 
entirely in the rear of the base of the dorsal fin extending to the end 
of the snout. What was my astonishnient on the following day, on 
turning over the young flounder on its left side, to find that the right 
eye had actually sunk into the tissues of the head, penetrating into 
the space between the base of the dorsal fin and the frontal bone, to 
such an extent that the tissues adjoining the orbit had slowly closed 
over a part of the eye, leaving only a small elliptical opening, smaller 
than the pupil, through which the right eye could look when the fish 
was swimming vertically. While the young flounder lay on its side, 
the right eye was constantly used in looking through the body, and 
could evidently see extremely well all that took place on the left side. 
On the following day the eye had pushed its way still farther through, 
so that a small opening now appeared opposite it, on the left side, 
through which the right eye could now see directly, the original 
opening on the right side being almost entirely closed. Soon after, 
this new opening on the left increased gradually in size, the right 
eye pushing its way more and more to the surface and finally looking 
outward on the left side with as much freedom as the eye originally 
on the left; the opening of the right side having permanently closed. 
I have thus in one and the same specimen been able to follow the 
passage of the eye from the right side to the left through the integu- 
ments of the head, between the base of the dorsal fin and the frontal 
