Methods of keeping and caring for dancers--Cages, nest-boxes, and materials for nest--Cleansing cages--Food supply and feeding--Importance of cleanliness, warmth, and pure food--Relations of males and females, fighting--The young, number in a litter--Care of young--Course of development--Comparison of young of dancer with young of common mouse-- Diary account of the course of development of a typical litter of dancers. CHAPTER III BEHAVIOR: DANCE MOVEMENTS Dancing--Restlessness and excitability--Significance of restlessness-- Forms of dance: whirling, circling, and figure-eights--Direction of whirling and circling: right whirlers, left whirlers, and mixed whirlers-- Sex differences in dancing--Time and periodicity of dancing--Influence of light on activity--Necessity for prolonged observation of behavior. CHAPTER IV BEHAVIOR: EQUILIBRATION AND DIZZINESS Muscular coordination--Statements of Cyon and Zoth concerning behavior-- Control of movements, orientation, equilibration, movement on inclined surfaces, climbing--The tracks of the dancer--Absence of visual dizziness--Comparison of the behavior of the dancer with that of the common mouse when they are rotated in a cyclostat--Behavior of blinded dancers (Cyon, Alexander and Kreidl, Kishi)--Cyon's two types of dancer-- Phenomena of behavior for which structural bases are sought: dance movements; lack of response to sounds; deficiency in equilibrational ability; lack of visual and rotational dizziness. CHAPTER V STRUCTURAL PECULIARITIES AND BEHAVIOR The functions of the ear--Structure of the ear of the dancer as described by Rawitz, by Panse, by Baginsky, by Alexander and Kreidl, and by Kishi-- Cyon's theory of the relation of the semicircular canals to space perception--Condition of the auditory organs--Condition of the equilibrational organs--Condition of the sound-transmitting organs--The bearing of the results of anatomical investigations upon the facts of behavior. CHAPTER VI THE SENSE OF HEARING Experiments on hearing in the dancer made by Rawitz, by Panse, by Cyon, by Alexander and Kreidl, by Zoth, and by Kishi--Hearing and the voice-- Methods of testing sensitiveness to sounds--Results of tests with adults-- Importance of indirect method of experimentation--Results of tests with young--The period of auditory sensitiveness--Individual differences. CHAPTER VII THE SENSE OF SIGHT: BRIGHTNESS VISION What is known concerning sight in the dancer--Brightness vision and color vision--Methods of testing brightness vision, the visual discrimination apparatus--Motives for discrimination and choice--Punishment versus reward as an incentive in animal experiments--Hunger as an incentive--An electric stimulus as an incentive--Conditions for brightness vision tests-- White-black vision--Evidence of preference--Check experiments--Conclusion. CHAPTER VIII THE SENSE OF SIGHT: BRIGHTNESS VISION (_Continued_)