152 



SCIENCE 



[N. S. Vol. XXVIII. No. 709 



cepting the belief that a fact of animal be- 

 havior can no longer be surely ascertained 

 by incidental observation. The tendency, 

 however, still to use the now often worthless 

 *' notes " of the nature lover and of the old- 

 time naturalist has not completely passed 

 away. For instance, whenever the psycholo- 

 gist needs to find facts concerning phylogen- 

 etic expressions of consciousness to illustrate 

 certain well-marked lines of development dis- 

 covered in the study of the growth of the 

 human mind, he is tempted to resort to the 

 use of this discredited material. The same 

 tendency is exhibited by the anatomists when- 

 ever there is need for correlating structure 

 with function. 



There is growing a stronger and stronger 

 inclination on the part of both the psycholo- 

 gists and the biologists, of this country at 

 least, to wait patiently for the much needed 

 information about the behavior of animals 

 until the student of behavior can supply it 

 by the use of experimental methods. The 

 process of obtaining facts in this way is ad- 

 mittedly slow; but to those who doubt that 

 there is growing up a body of studies, scien- 

 tifically made and controlled, we recommend 

 the perusal of Yerkes' book on the dancing 

 mouse. 



This book, while not broad in its general 

 implications, is nevertheless a study valuable 

 alike for its history of the development of 

 special problems in the study of animals and 

 for its account of the methods of solving them. 

 Were the book written wholly for the benefit 

 of the investigator trained in the field of 

 comparative psychology, it would need criti- 

 cism on the score of a too detailed description 

 of methods and apparatus which, later on in 

 the course of the study, are often discarded 

 for better ones. But this manner of presen- 

 tation has its advantages in that it shows to 

 the novitiate the difficulties and discourage- 

 ments which may lie in the way of the student 

 of behavior. 



The author begins his study of the dancer 

 by an introduction to the literature on the 

 origin and the life history of this interesting 

 animal. The historical research into the 

 origin of* the dancer indicates "that a struc- 



tural variation or mutation which occasionally 

 appears in Mu^ Musculus, and causes those 

 peculiarities of movement which are known 

 as dancing, has been preserved and accentuated 

 through seleetional breeding by the Chinese 

 and Japanese, until finally a distinct race of 

 mice which breeds true to the dance character 

 has been established." The age of the race is 

 not known, but it is supposed to have existed 

 for several centuries. 



In following chapters, the dance movement 

 is discussed in detail. After sifting the 

 anatomical evidence, Terkes concludes that 

 no structural variations existing in the ear 

 or in the central nervous system are suffi- 

 ciently pronounced to account for the dancer's 

 peculiar types of movement. Certain possible 

 peculiarities of structure appear when the 

 ear of the dancer is compared with that of 

 the common mouse, but these variations, at 

 least according to the researches of several 

 prominent investigators, consist neither in the 

 absence of certain of the semicircular canals 

 nor in the presence of neural degenerations 

 in the cochlea, vestibule and auditory path- 

 ways. Yerkes points out the fact that our 

 exact knowledge concerning the structure of 

 the auditory apparatus of the dancer is all 

 too meager. What apparent facts have been 

 brought out by certain investigators are hotly 

 contested by certain other investigators. 



The adult animals are totally deaf ; the tests 

 made in support of this point are complete 

 and adequate. The young animals, on the 

 contrary, do react to auditory stimuli during 

 the third week of life. In a few individuals 

 the response to such stimuli was not obtained 

 either at this or at a later age. The deafness 

 of the adults is especially interesting in view 

 of the fact that the young animals can hear 

 and that the cochlea even of the adults ap- 

 pears not to be degenerated. 



The main contributions to the field accruing 

 from Yerkes' book come from the tests of the 

 brightness and color vision of the dancer. 

 The dancer was found to be quite sensitive to 

 changes in brightness. It can readUy dis- 

 criminate white from black and, with some 

 difficulty, Nendel's gray paper No. 10 from 

 No. 20. After many tests, Weber's law was 



