PROCEKDINGS OF UNITED STATES NATIONAL MUSEUM. 323 



{Umbra limi [Kirt.] Giinther) which was frozeu within solid ice in an 

 aquarium-globe, three or four times, and each time regained its vitality 

 upon being thawed out. Instances similar to the foregoing can be ad- 

 duced indefinitely. 



*The only hyhernation which is definitely known to occur among 

 fishes, says Professor Goode, takes place in the fresh-water lakes and 

 streams of cold regions. The fishes are driven by cold into the deeper 

 waters, and there remain in a state of torpor, ijroportional in degree to 

 the amount of cold which they experience. Hybernation does not ap- 

 pear to be in any case a voluntary act. The fishes do not become 

 torpid of their own accord. They avoid it as long as they can, and 

 only succumb when they are deprived of the means of escape. They 

 never become torpid when there are greater depths to which they can 

 retreat. 



tDr. C. C. Abbott reports of the fresh- water mullet {Myxostoma 

 ohlongum): "No degree of cold seems to affect the movements of this 

 species, and hundreds can frequently be seen under the ice, moving 

 slowly along the bed of the stream, feeding upon the wilted remnants 

 of pond-lily and splatter-dock plants. * * * This applies also to 

 our common roach {Stilhe americana), which, to a less extent, braves 

 the chilling waters of our streams throughout the winter, and, in con- 

 sequence, suffers from the persecutions of the three species of pike 

 {Esox retieuJafus, fasciatiis, porosus) inhabiting our streams." 



J See also Mr. Eudolph Hessel's observations upon the winter torpor 

 of the carp. This appears to be a true hybernation, during which, al- 

 though the fish takes no food tn some climates from October until 

 March, there is no diminution in weight. 



On the other hand, fishes have been reported as living and thriving 

 in water at an exceedingly high temperature; high enough to produce 

 death by coagulation of the albumen in their blood and tissues, unless 

 there is some j)rovision by which their interior parts are maintained at 

 a temperature lower than that of the surrounding water. As the exist- 

 ence of any protection analogous to that afforded to mammals by the 

 function of perspiration and evaporation seems obviously impossible to 

 animals living in the water, it is difBcult to understand in what way 

 such a reduction in temperature can be produced and kept up. 



§ Thus, Humboldt and Bonpland observed living fishes in hot wat«r 

 thrown uj) from a volcano and showing a temperature of 210^* F. 



§ Deslbntaines found a Chromis in the hot springs of Cafsa, in Bom- 

 bay, the water in which showed 30° R. (97.5° F.), and Shaw afterwards 

 saw small mullet and perch in the same springs. {Travels in Bombay^ 

 folio, Oxon. 1738, p. 231.) 



* Goode, loc. cit. 



t Notes on some Fishes of the Delaware Eiver. United States Fish Commissioner'* 

 Report for 1875-7G, p. 82.5. 



tThe Carp and its Culture. Fish Commissioner's Report for 1875-76, p. 869. 

 $ Quoted by Yarrell, loc. cit. 



