42 Fish Cultural Association. 
(3.) Still another set of arguments is based upon the sup- 
posed hybernating habits of other species of fishes. Prof. Hind 
remarks: “In seas which are not ice-incumbered the winter 
torpidity of the mackerel may be of very short duration ; 
in ice-incumbered seas it may extend over several months. 
In this particular this mackerel resembles the sturgeon of 
the Caspian Sea, whose torpidity during the winter is well 
known, and this winter sleep is not confined to these fish, 
but is probably much more general than is usually sup- 
posed.”* Here we have a definite statement.. The mackerel 
hybernate, and the winter sleep is not confined to the mackerel. 
The only hybernation which is definitely know to occur 
among fishes takes place in the fresh-water lakes and streams 
of cold regions. The fish are driven by cold into the deeper 
waters, and there remain in a state of torpor proportionate 
in degree to the amount of cold which they experience. They 
may even be frozen up in the midst of a mass of ice and re- 
cover their vitality when the ice is melted. Mr. Milner had 
a mud-minnow (Uméra limi) which was frozen in solid ice in 
the middle of an aquarium globe three or four times, and 
each time recovered its vitality upon thawing out. Marine 
in the extreme north doubtless undergo similar experiences, 
fishes though I am not aware that any record of such a_phe- 
nomenon has ever been published. 
In warm regions an analogous phenomenon takes place, 
which has been called zstivation. When the lakes and streams 
are dried up by ‘the heat; ‘the/fish“seek refuge in therdeepest 
pools, and when these too are dried, they bury themselves in 
the mud at the bottom and remain torpid until the rainy sea- 
son refills the reservoirs and revives them. Hybernation and 
zstivation do not appear in any case voluntary acts. The fish 
* Parti peeel. 
