THE WINTER RETREAT OF THE FISHES. 63 



silent under a sheet of new ice, and not another mollnsk of any sort to 

 be found moving. 



Water mollusks, such as the river -mussels, the coil-shells, and the 

 thick-shelled Paludince, do not need to hibernate, because they are pro- 

 tected by the water always flowing over them, and need only sink in the 

 mud or go to a deeper part of the stream. 



After the invertebrates come in regular order the fishes, which are 

 affected only slightly by wintry rigors. The waters frequented by 

 many of the fishes of our inland streams are often only shallow rills, 

 that go nearly dry in the fall. I do not think, however, that the trout, 

 shiners, sunfish, minnows, darters, and the like, let themselves often get 

 caught by the ice at the head-waters of these small streams, for there the 

 ice would freeze fast to the bottom and might remain so for several 

 months. Nevertheless they may do so, and would no doubt survive it, 

 since some of them are accustomed to bury themselves deep in the sand 

 and mud at all seasons, and so can get along on a small and impure sup- 

 ply of water ; another of their habits is to congregate about springs bub- 

 bling up in the bottom of the stream. Moreover, experiments show that 

 fishes may be frozen into a block of ice, and still come out all right when 

 their prison thaws away from them. Thus it happens that small fishes, 

 overtaken by sudden hard frosts, could be frozen into the solid ice or 

 more solid sand of a brook-head, and remain there as stiff and dead as 

 sticks from December to March, yet prove alive and well enough when 

 the April sun honeycombs the ice and wakes them into new life. This 

 is a stoppage of vitality — a temporary death — somewhat different from 

 torpidity; moreover, there seems no limit to the time a fish might re- 

 main thus congealed and still recover, since no bodily waste goes on dur- 

 ing his confinement. 



The rule among fishes, however, is to run away from the shallows 

 as the chill of approaching winter begins to find them out, and to seek 

 waters deep enough to insure their not being frozen to the bottom. Un- 

 derneath the ice the water is none too cold for their comfort, the bottom 

 is free for them. to forage upon, plants, becoming greener and greener as 

 spring advances, give the vegetable-feeding species dainty meals of ever- 

 freshening sprouts, and various enemies, such as birds and boys, are shut 

 off from harming them. The amount of food consumed, however, is very 

 small. Thus, under the solid and storm-swept plain which covers the lake 

 and broad river, there is lived a peaceful, happy, industrious life in the 

 greenish twilight of undisturbed depths. 



