OF THE SWORDFISH. 
115 
the structure of the eye, belong exclusively to this class of 
animals ; and besides many general peculiarities, the eye 
presents in the individual species all the variety and irre- 
gularity which characterize the organs of animals low in 
the scale, and exhibits a gradual transition to the apparent- 
ly anomalous eyes of molluscous animals. The broad flat 
irregular form of the eye, and the quantity of matter inter- 
posed between the outer coat and the retina, in the sword- 
fish, closely resemble the appearances presented in the 
eyes of the Octopus and Loligo. From the great size 
and simple structure of this organ in fishes, a minute ex- 
amination of these peculiarities might throw much hght 
on the nature of many parts, the uses of which are still 
perfectly unknown in the higher orders of animals. The 
eye of the common swordfish appears not to have been 
hitherto examined ; and I am indebted for the opportunity 
of making the following observations to Professor Jame- 
son, who kindly presented me with the two recent eyes, 
and the whole of the viscera, of the beautiful male specimen 
of that rare animal, lately taken in the Frith of Forth, and 
now preserved in the Museum of the University. 
The eyes of the swordfish are so perfectly lateral in their 
position, and so flat anteriorly, that that animal can per- 
ceive objects only with one eye at a time. This is proba- 
bly another reason, besides those stated above, for the eyes 
of this fish being usually large. In the specimens I ex- 
amined, the transverse diameter measured S inches, the 
axis 2| inches, and the entire animal 7 feet 2 inches from 
the point of the sword to a line drawn between the tips of 
the tail. The general form of the eye is that of an irregu- 
lar hemisphere, a little depressed in the direction of the 
axis, the anterior part corresponding to the flat base of the 
hemisphere. The eye is circular round the axis, but its 
sphericity on the back part is very imperfect from the irre- 
H 2 
