CONTENTS V 



No. 4 



i. Pre-Thaeesian Philosophy 201 



Melanchthon F. Libby, Ph.D. 



Professor of Philosophy 



2. Sex Differences and Variability in Color Perception 207 



V. A. C. Henmon, Ph.D. 



Professor of Psychology 



3. Introduction to the Study of the Ants of Northern 

 Colorado 215 



W. W. Robbins, M.A. 



Instructor in Biology 



4. Remarks on Some Northern Colorado Plant Communities 

 with Special Reference to Boulder Park (Tolland, 

 Colo.) 223 



Francis Ramaley, Ph.D. 



Professor of Biology 



5. Notes on the Flow of Water in Irrigation Ditches . 237 



Clement C. Williams, C.E. 



Associate Professor of Civil Engineering 



6. Alphabetical Index 249 



