ing," or "in winter-sleep" deviates functionally from the normal; also, that the exact time of the observations be recorded. There is a certain amount of evidence that even birds, representing the highest type of activity, may possibly hibernate; and that many animals, not usually thus affected, may become so under exceptional circumstances—indeed, that man himself, owing to peculiar states of the nervous system, may pass into a condition ("trance") having much in common with the hibernation of lower animals. I think it is very probable that, when the matter has been fully investigated, all degrees of cessation of functional activity will be found represented, from the normal daily sleep of man and other animals, to the lowest degree of activity consistent with the actual maintenance of life. The flying squirrel is nocturnal in habits and exceedingly active, even in confinement, as Prof. Perkins (loc. cit.) has shown; but during the daytime it seems not to be correspondingly quick—in a condition, in fact, resembling somewhat that of a hibernating animal. The "diurnal hibernation" of the bat is not to be forgotten. I noticed that my chipmunk invariably, after feeding, tucked his head down and assumed a more or less ball-like form highly suggestive of a tendency to hibernation.
There are many questions that arise in connection with this subject, one of which bears directly on the subject of comparative psychology: How and to what extent is the intelligence of animals influenced by hibernation? It may be considered pretty clear that both the ground squirrel and the flying squirrel hibernate, and these are certainly among the lowest—perhaps are actually the lowest—in intelligence of the whole tribe. We know that struggle among higher animals develops mental adaptation and other forms of intelligence, and it is rational to suppose that those species of squirrels that do not hibernate throughout the winter, but endeavor to prevail over their surroundings, as well as to adapt themselves to them, should be more intelligent than those spending a large portion of each year in inactivity.
My chipmunk, during its captivity, under certain circumstances, kept to his original habits—e. g., when a single nut was given him he would eat it immediately, but if several were presented at once he would hide them one by one in a corner of his cage, or, if sufficiently small, pack them away in his cheek-pouches. He did the same with cereal grains. When cotton wool or web-like material was placed in the cage, he manipulated it a good deal, but finally made a bed of it, in which he buried himself out of sight.
Within the last ten years attention has been called to "singing" in certain rodents, especially mice; but from numerous references in the literature it appears that "singing," or something
