388 RUTH J. STOCKING 



est amount of attention, heritable abnormalities having been 

 but little studied. This paper presents an investigation of herit- 

 able abnormalities in Paramecium. 



The principal points examined in this presentation are the 

 following: The origin and nature of the abnormalities; their 

 relation to conjugation; their inheritance and variation in uni- 

 parental reproduction, with relation to the present day prob- 

 lems of 'pure line' work ; how precisely inheritance occurs ; whether 

 there are variations of kind and degree of abnormality; whether 

 such variations are themselves inherited; whether by selection 

 abnormal stocks multiplying asexually can be altered in their 

 hereditary characteristics or differentiated into two or more 

 hereditarily diverse stocks; their relation to biparental inherit- 

 ance; their relation to survival. 



Previous work on the abnormalities found in protozoa has 

 dealt mainly, as before remarked, with the results of environ- 

 mental action. Jollos ('13) subjected a race of Paramecium 

 caudatum to changes of temperature and obtained by this 

 method differences in size, as did Hertwig ('08), Popoff ('08, '09), 

 and Rautman ('09). Jollos found that these changes are transi- 

 tory and soon disappear as the paramecia become adapted to 

 their new conditions. In a short preliminary note, which does 

 not present the evidence for his conclusions, he states that in 

 one case he obtained a permanent change. He subjected a 

 race of Paramecium to a high temperature and obtained a race 

 which was permanently small at high, normal, and low tempera- 

 tures. Popoff ('09) was able to produce by experimental means 

 two abnormal races of Stentor, one giant and the other dwarf. 

 He centrifuged a dividing Stentor, and so caused an unequal 

 distribution of the nuclear material. The daughter cell which 

 received the smaller part was one-fourth the size of the cell 

 which received the larger part. These two multiplied nor- 

 mally for about a week and during that time retained their 

 abnormal sizes. The cultures were then lost. He obtained 

 another giant race of Stentor by suddenly cooling a dividing 

 individual. The division did not take place and the animal 

 reorganized into a single individual which grew and subsequently 



