STUDIES ON A RACE OF PARAMOECIUM POSSESSING 

 EXTRA CONTRACTILE VACUOLES 



I. AN ACCOUNT OF THE MORPHOLOGY, PHYSIOLOGY, GENETICS AND 

 CYTOLOGY OF THIS NEW RACE 



ROBERT T. HANCE 



Zoological Laboratory, University of Pennsylvania 



THREE PLATES AND TWELVE CHARTS 



CONTENTS 



I. Introduction 288 



II. Technique 288 



III. Morphology 291 



a. General description 291 



b. The vacuoles 292 



IV. Observations on the behavior of the vacuoles 294 



a. Percentages — range of vacuole number 294 



b. Change of number during the life time of the individual 297 



c. Number of vacuoles in offspring 298 



d. Effect of various conditions on vacuole number 299 



V. Physiology 303 



a. General 303 



b. Resistance 307 



c. Rate of vacuole contraction 307 



d. Conjugation 312 



VI. Genetic^ 314 



a. Inheritance of vacuoles for four generations 314 



b. Effect of selection 316 



c. The immediate and temporary effect of location of the vacuoles 



in the parent form on inheritance by offspring 320 



d. The effect of conjugation 320 



e. Attempts to cross the two races 323 



VII. Cytology ; 323 



VIII. Discussion 324 



IX. Summary 325 



X. Bibliography ; 327 



287 



