vm TABLE OF CONTENTS 



PAGE 



2. Blowfly Larvae — Musca sp. (?) 175 



a. Introduction; b. Locomotion; c. Accuracy of orienta- 

 tion; d. Orientation in light from two sources; e. Orien- 

 tation and movement — (ij perpendicular to the direc- 

 tion of the rays — (2) toward a source of light; /. Sen- 

 sitive region; g. Effect of light intensity on rate of 

 locomotion; h. Method; i. Mechanics of orientation; 

 j. Discussion; k. Summary. 



3. Earthworms : L98 



Summary 205 



4. Planaria 206 



Summary 210 



5. Echinoderms 211 



CHAPTER X 



Concerning the Question of Orientation in Mollusks, Arthropods 

 AND Vertebrates, with Special Reference to Circus Movements 

 • and their Bearing on this Question 



1. General Account of Orientation 214 



2. Circus Movements 215 



3. Frogs and Toads 218 



A. Bufo americanus. 



a. Method; h. Orientation in light from two sources; 

 c. Orientation with one eye destroyed. 



4. Caprella 223 



a. Orientation; h. Discussion. 



5. General Summary and Conclusions of Part II 228 



PART III 

 GENERAL CONSIDERATION OF REACTIONS TO LIGHT 



CHAPTER XI 



Adaptation, Formation of Aggregations in Regions of a Given Light 

 Intensity and Different Methods of Response in Attaining 

 this Region and Remaining in it. 



1. Introduction sho\\ing that Reactions in general are Adaptive. 236 



2. Different Reactions observed in the Process of Collecting in 



Regions having a given Condition of Illumination 239 



