AN EXPERIMENTAL STUDY ON THE LIFE-HISTORY 

 OF HYPOTRICHOUS INFUSORIA.^ 



BY 



LORANDE LOSS WOODRUFF. 



With 3 Plates and 12 Figures in the Text. 



I. Introduction 5^5 



n. General Methods and Technique 587 



III. Description of the Cultures 59° 



1. Oxytricha fallax, Culture A 590 



2. Oxytricha fallax, Culture B 594 



3. Pleurotricha lanceolata, Culture A 594 



4. Pleurotricha lanceolata, Culture B 596 



5. Gastrostyla steinii, Culture A 596 



IV. Discussion of the Data of the Cultures 601 



1. Rhythmical and Cyclical Variation in the Rate of Division 601 



2. Artificial Rejuvenescence 605 



3. Conjugation 606 



V. Physiological and Morphological Variation during the Life-cycle 607 



1. Physiological Variation 607 



2. Morphological Variation 608 



VI. Effect 01 Initial and Daily Stimulation with Salts on the Rate of Division 614 



1. Potassium Phosphate (Monobasic and Dibasic) 615 



2. Potassium Chlorid and Sodium Chlorid 620 



3. Potassium Sulphate and Magnesium Sulphate 621 



4. Potassium Bromid 622 



5. Comparison of Results 622 



Vn. Effect of Light on the Rate of Division 625 



Vm. Summary 626 



I. INTRODUCTION. 



The first suggestion of the cycHcal character of the Hfe-history 

 of Infusoria was advanced by Dujardin as an argument against 

 Ehrenberg's theory that the Protozoa, because of their simple 

 organization and method of reproduction, are not subject to 

 natural death. The observations of Biitschli ('76) and Engel- 



'Submitted in partial fulfilment of the requirements for the degree of Doctor of Philosophy, in the 

 Faculty of Pure Science, Columbia University. 



