380 Prof. J. C. Schiédte on the Development of 
men last described, on account of the change which is observed 
in the position of the left eye, which is now placed not only 
above the right eye, but at the same time a little behind it. 
The left eye is entirely transferred to the right side, though it 
stands so high on this side that its pigment, dimly shinin 
through the skin, can still be seen from the left side as a sma 
dark border. A striking evidence of its having receded further 
back is afforded by the fact that the first ray of the dorsal fin 
in this specimen stands so far forward, in comparison with the 
‘eye, that it is on a level with the middle of its left margin, 
whilst the third ray occupies the place relatively to the eye 
which in the former specimen is occupied by the frst ray. 
The specimens of young Hippoglossus pinguis which I 
have before me present a similar progressive development. 
The smaller is 57 millims. long. The outlines of all the super- 
ficial parts of the skull are distinctly seen through the skin, as 
well as the branches of the muciparous canal and their nume- 
rous ducts. The left eye is placed at the top of the head, so 
much inclined to the left (blind) side, that from the right side 
the iris is only partly visible, and the pupil altogether invisible; 
it is placed straight infront of and close to the dorsal fin, which 
points alongside the right margin of the pupil. On the head of 
a second specimen, which is nearly twice as large (100 millims.) 
the ducts of the muciparous canals are evidently more nume- 
‘rous, and the infraorbital branch on the left (blind) side, which 
on the smaller specimen appears curved, is here almost straight. 
It has got space to grow straighter; for on this specimen the 
left eye has moved across the head so much that it now inclines 
as much to the right side as formerly to the left; and whilst 
in the smaller specimen it stood nearly straight before the 
dorsal fin, the latter would, if prolonged in the larger speci- 
men, cross the eye just inside its left margin. That the 
eye is under pressure, wedged in between the interspinous 
part of the dorsal fin and the anterior frontal bones, is evident 
from an indenture in its outline on the posterior margin; and 
this pressure evidently cannot cease tilt the eye, gliding still 
further to the right, has got clear of the dorsal fin. 
In order to explain how the upper eye of the Pleuronectide 
comes into that position relatively to the dorsal fin which it 
occupies in the adults, naturalists have had recourse to the 
hypothesis that the dorsal fin prolongs itself in a forward 
direction when the upper eye, by the torsion of the head, has 
come into its final place. ‘This hypothesis was first proposed 
by Van Beneden (Ann. Sc. Nat. sér. 3. t. xx., “ Note sur la 
Symétrie des Poissons Plewronectes dans leur jeune age,’ p.342), _ 
and has been adopted also by Dr. Traquair, in his exhaustive and 
