UNIVERSITY OF CALIFORNIA PUBLICATIONS 



ZOOLOGY 



Vol. 16, No. 16, pp. 241-292, plates 18-23 



ON THE LIFE-HISTORY OF A SOIL AMOEBA 



CHARLIE WOODRUFF WILSON 



CONTENTS 



PAGE 



A. Introduction 242 



I. Historical 242 



II. Material and method 243 



B. Observations 245 



I. The trophozoite 245 



1. Movement 245 



2. Morphology 246 



3. Binary fission 247 



(a) Prophase 247 



( 6 ) Metaphase 247 



(c) Anaphase 248 



(d) Telophase 248 



(e) Nuclear reorganization 248 



(f) Cytoplasmic division 249 



(g) Behavior of organelles in mitosis 249 



(ft) Mitosis and amitosis 254 



4. Multiple fission 255 



5. Budding 256 



6. Chromatin extrusion 258 



(o) Chromidial formation in cysts 258 



(6) Chromidia in other amoebas 259 



((') Significance of the chromidia 260 



II. The cyst 261 



1. Characters 261 



2. Encystment 263 



3. Excystment 263 



IIL The flagellate 264 



1. Morphology 267 



(a) Process of enflagellation 268 



(6) Process of exflagellation 269 



0. Sexual stages in cultures 269 



D. Comparison with related amoebas 271 



E. Systematic position 272 



F. Summary 276 



G. Literature cited 278 



