AUTHOR S ABSTRACT OP THIS PAPER ISSUED 

 BY THE BIBLIOGRAPHIC SERVICE, OCTOBER 13 



AN EXPERIMENTAL STUDY OF AN AMICRONUCLEATE 

 OXYTRICHA 



I. STUDY OF THE NOKMAL ANIMAL, WITH AN ACCOUNT 

 OF CANNIBALISM 



J. A. DAWSON 



Oshorn Zoological Laboratory, Yale Universihj 



TWENTY FIGURES 



CONTENTS 



1. Introduction 473 



2. Material and methods 475 



3. The normal animal 477 



1. History of culture A 479 



2. Attempts to obtain conjugation 482 



3. Cytology of Oxytricha hymenostoma 483 



4. Cannibalism 485 



1. Observations on the process of swallowing 486 



2. Digestion of the ingested animals 490 



3. The effect of the culture medium 494 



4. The physiological effect of cannibalism 498 



5. Discussion 503 



6. Summary 506- 



1. INTRODUCTION 



The presence of a macronucleus and a micronucleus has long 

 been recognized as one of the striking features which aids in 

 marking off the Infusoria from the rest of the Protozoa, and there 

 is abundant evidence tending to prove that the micronucleus is 

 an indispensable part of the organism during both conjugation 

 and endomixis. In all the ciliates where the micronucleus has 

 seemed to be absent in the vegetative stages of the life history, 

 a careful study has invariably revealed its presence at the onset 

 of sexual phases. 



473 



