4 CONTENTS. 



Notes on the Nesting Activities of the Noddy and Sooty Terns — Continued. Page. 



Recognition of the young 76 



Instinct and habit in the nesting activities 80 



Modifiability of instinctive activities 80 



Integration of complex habits 82 



Studies on the Spectral Sensitivity of Birds 85 



Methods of studying spectral sensitivity 87 



The limits of the chick's spectral sensitivity 90 



Limits at the Red end 91 



Limits at the Violet end 94 



Relative stimulating effect of monochromatic light 96 



R^sum6 of results of study on chick 98 



Limits of spectral sensitivity in the Homing Pigeon 99 



Limits at the Violet end 99 



Limits at the Red end 101 



R^sum6 of Tests on Pigeon 104 



The Acquisition of Skill in Abchery 105 



Equipment 108 



Computation of averages and comparison of individual and group records 109 



A comparison of unlike groups of individuals under the same conditions of 



practice Ill 



Distribution of practice and rate of learning 1 13 



Purpose and method of the experiment 113 



Comparabihty of the groups studied 114 



Conditions affecting improvement 116 



Effect of the distribution of practice 120 



The problem of "distribution-rate" relation 124 



R6sum^ of results 127 



Bibliography 128 



