THEORIES OF MIGRATION 19 



as the only result. Those to whom the theory of 

 submersion in marshes did not appeal stated that 

 swallows and swifts remained in a torpid state in 

 hollow trees or clefts in rocks; and numerous per- 

 sons in our own country have related with great cir- 

 cumstance the finding of such birds, the manner of 

 their reviving, and their subsequent death if not 

 permitted to resume their slumbers. Even the cau- 

 tious Coues apparently was inclined to place a cer- 

 tain amount of behef in hibernation, mainly since in 

 his day the chimney swift disappeared in the 

 autumn to some unknown place. 



As final comment, attention may be drawn to the 

 fact that hibernation, or its correlate aestivation, is 

 of common occurrence among mammals, reptiles, 

 and amphibians, and even among fishes, if we accept 

 the burrowing of lung-fishes and of some forms of 

 minnows in moist mud during periods of drought as 

 related to the phenomenon under consideration. It 

 is strange indeed, therefore, that hibernation in 

 birds has never yet been scientifically proved in 

 spite of the many cases that have been claimed. The 

 frequent connection of this superstition with swal- 

 lows is probably explained by the fact that these birds 

 regularly resort to growths of rushes in marshes and 

 swamps for roosts and shelter during late summer 

 and autumn, and that during storms many perish, 

 and fall into the mud and water, but never revive 

 on the approach of more clement weather. 



