BIPARENTAL INHERITANCE IN PARAMECIUM 423 



for US to determine the average differences between the indivi- 

 duals representing the same sex; between the diverse 'females,' 

 and between the diverse 'males.' If the differences between the 

 two members of pairs are not distinctly greater than those between 

 members of admittedly the same sex, then a fortiori these would 

 constitute no basis for holding the two members to be sexually 

 different. 



With these considerations in mind we may examine the data. 



Miss CulVs experiment 



In Miss Cull's experiment it was found that there is in most 

 cases a difference between the two ex-con jugants with respect to 

 vigor and reproductive power. 



At the end of the month, of the 65 pairs then represented by living 

 cells, in twenty-seven pairs, or 41 per cent, one of the exconjugants only, 

 or the off-spring from it were alive; in fifteen pairs, or 23 per cent, the 

 }:)rogeny of one exconjugant was three times as large as that of the other; 

 in six pairs, the descendants of the one were twice as numerous as those 

 of the other organism; and in only five cases had both conjugants given 

 rise to the same number of offspring. The twelve remaining pairs 

 showed a •wdde diversity in the number of paramecia produced by any 

 two conjugants. (Cull '07, p. 88). 



The differences were determined by examining the number of 

 progeny present in the vial culture at the end of the month. 



It needs to be remembered that a single additional fission 

 doubles the number of progeny in one conjugant as compared with 

 the other; so that a doubhng of the number of progeny by no 

 means signifies a large difference in the rate of fission, in the course 

 of a month, or even in the course of a few days. Such a difference 

 in the number of progeny might be produced even though the 

 rate of fission in the two were only slightly cUfferent. Now, we 

 have no further statistics on this case, for determining how far 

 there are variations in the rate of fission even when we take the 

 organisms quite at random, so that we cannot tell how the differ- 

 ences between the members of pairs compare with the differences 

 we should find if we took two individuals at random. 



THE JOURNAL OF KXPERIMENTAL ZOOLOGY, VOL. 14, NO. 3 



