EXPERIMENTS ON THE REPRODUCTION OF THE 

 HYPOTRICHOUS INFUSORIA 



II. A STUDY OF THE SO-CALLED LIFE CYCLE IN OXYTRICHA FALLAX 



AND PLEUROTRICHA LANCEOLATA 



GEORGE ALFRED BAITSELL 



Theresa Seessel Felloxo in Zoology 

 Osborn Zoological Laboratory, Yale University 



SIXTEEN FIGURE^ (ONE PLATE) 



CONTENTS 



I. Introduction... . 211 



II. Methods 213 



III. History of the cultures 214 



1. Oxytricha fallax 214 



a. Culture Ob 214 



b. Culture Oh 215 



c. Culture Ove : .... 215 



d. Culture Obtt 217 



2. Pleurotricha lanceolata 219 



a. Culture Ph 219 



b. Culture Pb 220 



c. Culture Phtt 220 



IV. Prepared material 223 



1. Oxytricha fallax 223 



2. Pleurotricha lanceolata 224 



V. Discussion and conclusions 225 



VI. General summary 230 



Literature cited _. 233 



I. INTRODUCTION 



As is well known,. the early experimental work with the Infu- 

 soria gave evidence which was interpreted as supporting the 

 view that these unicellular forms possess a definite life cycle 

 comprising the generations between two successive conjugations, 

 and on this account they can pass through but a certain number 

 of generations, in the absence of conjugation, without senes- 

 cence and death occurring. Calkins' work ('02) showed that 



211 



