INHERITANCE IN ABNORMALITIES 445 



fully accomplished in twenty-five races; from each of these were 

 isolated two sorts of lines, one quite normal, the other continu- 

 ally producing abnormalities — ^the two cultivated side by side. 



Calkins and Gregory ('13) have in some cases obtained four 

 diverse races from the four primary daughter cells, or 'quad- 

 rants' of an exconjugant — these being the four individuals that 

 receive the four macro-nuclei produced before fission occurs. It 

 is to be noted that our selection resulting in the isolation of 

 lines differing hereditarily in abnormality has often been brought 

 about much later in the series of generations, so that the differ- 

 entiation has occurred within the compass of a single 'quadrant,' 

 or indeed within a much narrower fraction of the descent. In 

 several cases differentiation through selection did not begin till 

 after several weeks had passed with production of a great num- 

 ber of generations. Thus the results of selection in the present 

 case cannot be interpreted as due to a primary difference in the 

 four original macronuclei produced during conjugation. Selec- 

 tion is effective when begun with progeny of a single individual 

 that has appeared many generations after conjugation. 



4. In a race of Paramecium which upon extended examina- 

 tion shows no hereditary abnormalities, conjugation results in 

 the appearance of many lines which are hereditarily abnormal, 

 others which are normal throughout (Experiment 2). 



This is of course an example of what Jennings ('13) has de- 

 scribed as the 'production of variation by conjugation.' It 

 appears to fully meet the desire of Dobell ('14, p. 172) for 

 "convincing evidence of a concrete instance in which from a 

 known race — constant in a certain character — a new race — per- 

 manently diverse in this character — ^has arisen as a result of con- 

 jugation." For in Experiment 2, from a clone with a constant 

 character of normality (as shown by the progeny of the 54 split 

 pairs of this clone) 101 races which were permanently diverse 

 from the original one, being hereditarily abnormal, arose as a 

 result of conjugation. 



5. In the diverse lines descended from the different exconju- 

 gants of a conjugating culture, the two lines descended from 

 the two individuals that have conjugated together tend to be 



