UNIVERSITY OF CALIFORNIA PUBLICATIONS 



IN 



ZOOLOGY 



Vol. 18, No. 11, pp. 171-238, plates 6-8, 2 figures in text March 8, 1918 



THE FACTORS CONTROLLING THE DISTRIBU- 

 TION OF THE POLYNOIDAE OF THE PACIFIC 

 COAST OF NORTH AMERICA 



BY 



CHRISTINE ESSENBERG 



CONTENTS 



PAGE 



A. Introduction 271 



B. Acknowledgments 273 



C. Polynoidae and their general distribution 174 



I. Horizontal distribution 174 



II. Bathymetrical distribution 179 



1. Littoral species 182 



2. Deep-water species 183 



D. Factors controlling distribution 191 



I. Temperature in relation to depth and latitude 191 



II. Temperature as factor controlling distribution 200 



III. Role of currents in distribution 206 



IV. Winds 208 



V. Chemical composition of water 209 



VI. Food habits and mode of life 210 



VII. Plasticity 213 



E. General discussion 221 



F. Summary 229 



G. Literature cited 231 



H. Explanation of plates 234 



A. INTRODUCTION 



Polychaetous annelids date back at least to the Cambrian era, fossil 

 annelids representing several groups, some of which are similar to 

 modern annelids, having been found in the mid-Cambrian rocks (Wal- 

 cott, 1911 ) . The geological studies of the distribution of annelids seem 



