The Migration of Fishes. 43 
do not become torpid of their own volition. They avoid it as 
long as they can, and only succumb when they are deprived 
of means of escape. They never become torpid when there 
are greater depths to which they can retreat. 
(4.) Professor Hind lays much stress upon the presence of 
a “film” over the eyes of the spring and the autumn mack- 
erel and upon their alleged capture in winter in the waters 
of the Dominion, and also quotes arguments for hybernation, 
based upon the resemblance of the mackerel to the batra- 
chians (which are known to be capable of hybernation) in 
color, and upon its resemblance to embryonic forms of other 
fishes, which is supposed to “prove him low in the scale of 
intelligence.”* To the latter it is needless to refer. The so- 
calied “film” on the eye is not peculiar to the mackerel. 
_ Many fishes, such as the shad, the alewife, the menhaden, the 
bluefish, the mullet, the lake white-fishes, and various cyprinoid 
fishes, have a thick, tough membrance covering the anterior 
and posterior angles of the orbits, narrowing the opening to 
the form of an ellipse, with a vertical major axis. This pos- 
sibly becomes somewhat more opaque in seasons of decreased 
activity. It has never been observed to cover the whole eye. 
Until the fact has been established that “a skin forms over 
the eye” in winter, it is quite unnecessary to propose the 
theory that such a skin “is probably designed to protect that 
organ from the attacks of the numerous parasitical crustaceans 
and leaders which infest the external portions of the bodies 
of fishes, and are also found internally, as in the gills of 
codfish.’’+ 
mAPart ep. 79: t Hind, op. cit., Part II., p. 11. 
