414 POPULAR SCIENCE MONTHLY. 



from 'improving' each 'shining hour.' The rest of young animals 

 and children is quite as characteristic as their work or play. And we 

 must be careful not to derive too much of our evidence from captive 

 animals and restrained or metamorphosed children. We lack, too, 

 authoritative delimitations of the periods of activity and of rest of 

 animals. Groos,* in his discussion of the play of animals, has little 

 to say on this question other than the remark : " Of children and young 

 animals it is true that, except when they are eating, they play all day, 

 till at night, tired out with play, they sink to sleep." But there are 

 night-animals, and to a certain extent, night-men, for the evening 

 activities of the kitten, e. g., are often paralleled completely by those 

 of her young mistress. 



Of the lowest stages of animal life practically continuous activity 

 has been asserted. Dr. Hodge and Dr. Aikins,* in their study of 

 ' The Daily Life of a Protozoan,' observe : " A Vorticella works con- 

 tinuously, and shows in its life no period of inactivity or rest corre- 

 sponding to periods of rest in higher animals. In other words, a 

 Vorticella never sleeps." But this is only under absolutely favorable 

 conditions of life, for the same authors, a little further on speak of a 

 stage of rest or encystment : " Encystment is, therefore, of the nature 

 of an enforced ' rest,' a period of inactivity imposed by exceptional 

 external circumstances." 



As we go up the scale noticeable activity and inactivity increase in 

 their rhythmic alternations. The fishes and lower vertebrates sleep 

 periodically, and alternate their rest and exertion. Professor McGee 

 characterizes the intensified activity with long intervals of inertness 

 exemplified by the Seri Indians as ' simulating the habits of carnivorous 

 and other lower animals.' The life history of the lion and the tiger, 

 the elephant and the camel, the horse and the buffalo, to say nothing of 

 other and smaller animals, furnishes us with much evidence in point. 

 The anthropoids also, though not at all studied with reference to this 

 theory, may afford a valuable quota of proof. 



With many animals hibernation, and with many others aestivation, 

 occupies a considerable portion of their lives, the length and broken 

 or unbroken character of the ' sleeps ' or ' rests ' depending to some 

 extent upon climate, species, individuality. How far these ' sleeps ' 

 interfere with or improve the physical and mental faculties of such 

 animals during their season of real activity is not altogether clear, 

 but since hibernation and aestivation must at one time have been factors 

 in the survival of the fittest, they cannot have worked entirely to the 

 detriment of the creatures concerned, even in later days. And the 

 same may be said of the ' winter-sleep ' of the Eussian peasants. 



*'The Play of Animals.' Transl. by E. Baldwin (N. Y., 1898), p. 20. 

 * Amer. Journ. of Psychol, Vol. VI. (1895), p. 530. 



