HISTORY OV THE AMERICAN MENHADEN. 59 



outside to deposit tbo spawn. Or there may be a sort that never go as 

 far east or west as the others, but winter along our shores," &e.: while 

 Dr. Gilpin expressly remarks that though the asserted torpirWy and 

 blindness favor the idea of hibernation, he does not think that we have 

 vet suflBcient i)roof to assert them as facts. 



The authorities quoted in su|)port of the hibernation theory do not 

 in fact support it, and the testimony cited by Professor Hind is merely 

 tradition and i)opular oi)inion, some obtained dir(g;tly, the remainder at 

 second-hand. 



(3.) 8till another set of arguments is based upon thesuppose<l hibernat- 

 ing habits of other species of fishes. Professor Hind remarks: '• in .st;as 

 which are not ice-encumbered the winter torpidity (of the mackerel) may 

 be of very short duration; in ice-encumbered seas it may extend over 

 .several months. In this particular the mackerel resembles the sturgeon 

 of the Caspian Sea, whose torpidity during winter is well known, and 

 this winter sleep is not confined to these fish, but is probably much more 

 general than is usually supposed."* 



Here we have a definite statement. The mackerel hibernate, and the 

 winter sleep is not confined to the mackerel. 



The only hibernation which is definitely known lo occur among fishes 

 takes ])lace in the fresh-water lakes and streams ol cold regions. The 

 fish ;ire 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 

 ex[)('rieuce. They may even be frozen up in the midst of a mass of ice 

 and lecover their vitality when the ice is melted, t 



In warm regions an analogous phenomenon takes place which has 

 been called iestivatiou. When the lakes and streams are dried ui) by 

 the heat the fish seek refuge in the deepest pools, and when these too 

 are dry they bury themselves in the mud at the bottom and remain 

 torpid until the rainy si-ason refills the reservoirs and revives them. 



Fishes in the extreme north doubtless undergo similar experiences, 

 though I am not aware that any record of such a phenomenon has ever 

 been published. 



Hibernation and aestivation do not appear to bo in any case voluntary 

 acts. The fish do not become torpid of their own volition. They avoid 

 it MS 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. | 



* Part II, p. 11. 



•Mr. Milner had a mud-niinnow {Umbra liini) which was frozen in solid ice in the 

 middle of an aquarium globe three or four times, and each time recovered its vitality 

 upi.n, rhawiug out. 



t 'A curious phenomenon in Indian fresh waters, and one which has never been sat- 

 isfactorily explained, is the sudden appearance of healthy adult lishes after a heavy 

 fall <>f rain, and in localities which for months previously had been dry When i)iece8 

 of wiiter inhabited by fish yearly dry up, what becomes of them ? On January 1 8, 186l>, 

 when examining this question, I was taken to a tank of perhaps an acre in ex'ent, but 



