VARIATION AND INHERITANCE IN ABNORMALITIES 



OCCURRING AFTER CONJUGATION IN 



PARAMECIUM CAUDATUM 



RUTH J. STOCKING 



From the Zoological Laboratory of the Johns Hopkins University^ 



TWENTY FIGURES 



CONTENTS 



I. Introduction 387 



II. Methods 390 



III. Experimental Cultures 391 



IV. Types of Abnormal Races 397 



V. Nature of the Abnormalities 407 



VI. The Abnormalities as Hereditary Characters: 



Variation, Inheritance, and Selection 412 



Experiments in Selection 414 



■ Relation to Biparental Inheritance 440 



VII. Summary and Discussion of Results 444 



VIII. Literature 449 



I. INTRODUCTION 



The fact that there are two kinds of teratological variation, 

 one caused by gametic constitution and therefore heritable, the 

 other occasioned by the action of environmental conditions, and 

 not heritable, has been recognized for some years. There was 

 for a time an endeavor on the part of many investigators to show 

 that all abnormalities were due to conditions of nurture; but the 

 discovery of the strict mendelian inheritance of a large number of 

 malformations has overthrown that theory. In many of the 

 metazoa both kinds of teratological variation, gametic and en- 

 vironmental, have been studied, and their causes and behavior 

 partly determined. In the protozoa the abnormalities caused 

 by the action of external factors have received by far the great- 



^ Part of the work here reported was completed while the author held the 

 Alice Freeman Palmer Research Fellowship of Wellesley College. 



387 



THE JOURNAL OF EXPERIMENTAL ZOOLOGY, VOL. 19, NO. 4 

 NOVEMBER, 1915 



