36 Herbert Eugene Walter 



B In changing directive light 87 



Changes in intensity 87 



Changes in direction 88 



Summary 89 



C In combination with other responses 89 



Geotaxis 90 



Thigmotaxis ' 92 



Goniotaxis 94 



Chemotaxis 94 



Summary 96 



3 Kinds of behavior 97 



A Generic and specific behavior 98 



Percentage of negativeness 98 



Character of the course in directive light 99 



Duration of movement 105 



Degree of wandering 106 



Rate of locomotion 107 



Time required to'leave a unit circle 107 



The effects of fatigue 108 



Responses to changes in intensity 109 



Manner of coming to rest no 



Summary 1 10 



B Individual behavior Ill 



Rate on successive days 113 



Relative value of individual behavior 112 



A cave planarian 114 



Summary 116 



(Pages 1IJ to 162 are printed in vol. v. no. 2) 



4 Basis of behavior 117 



A Morphological basis of behavior 117 



a General form of the body 118 



b Photoreceptors 122 



Summary 127 



B Physiological basis of behavior 128 



a Classification of physiological states 129 



b Changes in physiological states induced by light 130 



Effect of different intensities 130 



Effect of excessive light 131 



Effect of sudden change in light conditions 131 



Effect of continued exposure to light 131 



Effect of previous exposure to dark 132 



Summary 133 



C Psychological basis of behavior 134 



a How much can planarians see ? 134 



b Are planarians able to learn ? 135 



Summary 138 



