1876. ] The Development of Flounders. TOT 
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. Ihave 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 integuments 
of the head, between the base of the dorsal fin and the frontal 
bone. 
This observation leads to somewhat different conclusions from 
those of Steenstrup, who thought he could prove (from an examina- 
tion of alcoholic specimens) that the eye from the right side passed 
under the frontal bone. This is evidently not the case here, the 
eye passing round it, there being only a very slight torsion of the 
frontal in this young stage. Although at first glance this appears 
~ Soradically a different method of transfer of the eye from the ar 
described above, yet if the dorsal fin had not extended beyon 
_ the posterior edge of the right orbit the process would have me 
the same, as is readily seen. I hope soon to give full details, wi 
3 illustrations, of the process of transfer of the eye in its different 
Stages, in a paper I am preparing on the young stages of a few 
of our bony marine fishes. = ie 
But while I have thus been able to trace step by step m sa 
Specimens the transfer of the eye from one side to the 3 ir 
fan give no explanation of the cause which compels foun 
lie on their side. The explanations usually given are a “ is- 
factory - For the great depth of the body, the position of tao oom 
“land of the ventral fins, the undulating mode of miie 
all these are so many causes specially adapted to enable t et? 
Swim in a vertical position. In fact, they cig cap icant cept 
M young stages, when their capacity for vertical mp is 
finitely less than when they commence to lie pu one side. 
