382 On the Position of the Eyes in Pleuronectide. 
14 millims., and 40 millims. long, that the development of the 
position of the eyes after hatching is upon the whole a very 
slow process, and that consequently the position of the eye on 
the future blind side can searcely have been quite symmetrical 
even in the new-born fish. In the young fish of 10 millims. 
length the anomalous eye has already, in every essential par- 
ticular, the same position with regard to the bones of the skull 
as in the adult, being placed in its orbit; and I therefore con- 
sider it in the highest degree probable that the arrangement 
of the frontal and anterior frontal bones round the eye of the 
future blind side takes place in all essential points already in 
the embryonal state; nor could the matter very well be ima- 
gined otherwise according to all we know about the formation 
of the embryo. But then the whole case falls under a very 
well-known biological law, and becomes plain enough. The 
young Plewronectide are born with a position of their eyes 
ealculated for life nearer the surface of the water, and grow 
slowly and gradually more asymmetrical in proportion as the 
adult fishes seek more the bottom of the sea, or, at any rate, 
are more calculated upon movement along a firmer surface *. 
Hence the well-known long series of forms exhibiting a gra- 
dual transition, from Hippoglossus pinguis, which does not in 
any considerable degree alter the shape in which it leaves the 
ovum, to the soles, which are entirely thrown on one side. It 
appears, however, that Hippoglossus pinguis is not the least 
asymmetrical form ofthe family. [have before me two perhaps 
not quite adult specimens of an apparently undescribed oceanic 
flounder, taken in the Atlantic, which I propose to call Bas- 
eanius tedifer, n.s., and which, in the series above alluded 
to, would take place before the Hippoglossus. It is, as is the 
case with other oceanic animals, clear as water, very high and 
narrow, about 25 millims. long, foliaceous, almost symme- 
trical; only the left side is a little more developed, and the 
eye on that side is placed a little lower on the head. The 
greatest height of the body is at the commencement of the 
anal fin, where it almost reaches one-half of the total length. 
The muciparous canal makes a very slight bend over the 
pectoral fin. ‘The dorsal fin reaches the nostrils in front, and 
approaches behind (as also does the anal fin) close to the caudal 
fin, which is slightly rounded at the end; the open space be- 
tween the ventral fin and the anal fin is longer than the 
ventral fin itself. The rays of the fins exhibit only few 
and long joints; their number I find to be in my two spe- 
* Monstrosities, caused by the eye of the blind side being arrested in 
its process of transfer in front of the dorsal fin, have long been known. 
Comp. Dr. Traquair’s treatise, p, 265. 
