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THE AMERICAN NATURALIST [Vol. XLII 



at least not as we do; that most of their apparent discrimina- 

 tion of color is due to differences in brightness; and that the 

 brightness of different colors is not the same for them as for 

 ourselves. 



It is extraordinary that the mice were unable to discriminate 

 the portals by different shapes of cards or of lights. They 

 showed no power of distinguishing forms. 



We have given some samples of Yerkes' methods and results; 

 many other matters of equal or greater interest were studied, 

 by varied methods, including the classic one of using labyrinths. 

 The author's experiences are set forth in interesting chapters 

 on educability, methods of learning, the efficiency of different 

 methods of training, the duration of habits, the revival of lost 

 habits, individual differences in behavior, and the like. When 

 it comes to responding to experimentation, the dancing mouse 

 is, as its name indicates, rather an artistic than a strictly utili- 

 tarian animal, giving a delightful variation from those orthodox 

 creatures whose main desire is to "get there," so that results 

 are not readily expressed correctly in terms of minutes required 

 and space passed over. "Most mammals which have been 

 experimentally studied have proved their eagerness and ability 

 to learn the shortest, quickest, and simplest route to food with- 

 out the additional spur of punishment for wandering. With 

 the dancer it is different. It is content to be moving; whether 

 the movement carries it directly to the food-box is of secondary 

 importance. On its way to the food-box, no matter whether the 

 box be slightly or strikingly different from its companion box, 

 the dancer may go by way of the wrong box, may take a few 

 turns, cut some figure-eights, or even spin like a top for a few 

 seconds almost within vibrissa-reach of the food-box, and all 

 this even though it be very hungry." 



In addition to the strictly experimental work, Yerkes gives 

 a full account of the peculiar "dancing" movements that have 

 given the animal its name; a sketch of what we know of its 

 history, and an extensive discussion of the disputed question 

 as to whether its ears are defective and whether it is deaf. 

 Yerkes concludes that it can hear only for a few days, when 

 about two weeks old. 



Altogether, Dr. Yerkes' book is one of the most attractive 

 as well as one of the most valuable of the strictly scientific 

 studies of animal behavior. It would be venturing out of the 



