(lis 



THE AMERICAN NATURALIST 



[Vol. L 



while food is plentiful. Allen Cleghorn 30 (1910) ques- 

 tions the lack of food as a factor in producing lethargy 

 because spermophiles and marmots hide away for winter 

 when their food supply is at its best. In British Colum- 

 bia he finds that these animals retire a month earlier in 

 the lowland than at the timber line because, he thinks, in 

 the latter region they have not had time to acquire enough 

 fat, since at the timber line they come out of hibernation 

 later in the spring. Thus it is not clear exactly what part 

 food plays in the production of this dormant state. 



Treviranus 69 (1802) said that the cause of torpidity 

 during winter lies in the ability to live with all the vital 

 processes at a minimum. This is an acquired character 

 resulting from the habit of sleeping during winter, as is 

 evident, he thought, from the fact that it is lost in mar- 

 mots kept in captivity. The earlier opinion of Barton 70 

 (1799) was that it is an accidental circumstance and not 

 a specific character. The general idea, however, that 

 some sort of instinct, in connection with other factors, is 

 involved, was held by Eeeve 16 (1803), Barkow 15 (1846), 

 Claparede 29 (1905) and others. Desjardine 71 (1843) 

 thought that the need for sleep in rodents is as great as the 

 necessity of migration in birds. Blandet 25 (1864) de- 

 scribed winter-sleep as a relic— an echo from remote 

 periods when this phenomenon was general, having de- 

 veloped as a result of winters so severe that unless this 

 conserving process was resorted to, the animals would 

 have perished. Hibernation is thus, according to this 

 author, the effect of habit and annual periodicity. It still 

 persists in certain animals, but will soon become extinct. 

 Brunelli 28 (1902) believes that this tendency is the result 

 of a long period of evolution favored by the nature of the 

 burrow, etc., where hibernation takes place. But accord- 

 ing to Albini 68 (1894) the factors aiding this evolution are 

 not remoteness or other conditions of the burrow, but the 

 immobility of the animal. Carlier 72 more recently (1911) 

 classifies hibernation with estivation (summer-sleep) and 

 migration. Winter-sleep in mammals like the instinct 



