INHERITANCE OF SIZE IN PARAMECIUM 199 



experiment (as shown in table 51 of the previous paper). The 

 correlation of the two members of the pairs (a and b) in number of 

 fissions for twenty days is found to be 0.4439 ± 0.0584. This is 

 almost exactly the same coefficient as that found for the entire 

 358 lines that lived through the twenty days; this, as shown in 

 our former paper ('13), was 0.4793 ± 0.0275. The agreement 

 between this value found for the 86 lines considered in the present 

 paper, with that for the 358 lines of the entire experiment indi- 

 cates that these 86 lines form a typical sample of the population, 

 and that therefore the value found for the correlation of a and b 

 in length would not have differed significantly if we had included 

 representatives of a larger number of pairs. We may, therefore, 

 conclude with confidence that the correct value of the correla- 

 tion in mean size between the descendants of pairs for this case is 

 close to 0.5744. 



SUMMARY 



As a result of conjugation the progeny of the two individuals 

 that have conjugated become more alike in their average length, 

 so that biparental inheritance occurs in respect to body size (as 

 well as in respect to rate of fission). The members of pairs in 

 the culture examined showed, owing to assortative mating, a co- 

 efficient of correlation in body length of 0.3881 ; this was increased 

 as a result of conjugation to such an extent that their progeny 

 showed a coefficient of 0.5744 — an increase of 48 per cent. 



April 4, 1913 



LITERATURE CITED 



Jennings, H. S. 1911 Assortative mating, variability and inheritance of size, 

 in the conjugation of Paramecium. Jour. Exp. Zool., vol. 11, pp. 1-109. 



Jennings, H. S., and Lashley, K. S. 1913 Biparental inheritance and the ques- 

 tion of sexuality in Paramecium. Jour. Exp. Zool., vol. 14, pp. 393-466. 



Pearl, R. 1907 A biometrical study of conjugation in Paramecium. Biomet- 

 rika, vol. 5, pp. 213-297. 



