-INHERITANCE OF SIZE IN PARAMECIUM 



195 



TABLE 2 



Correlation table for the measurements in length of the members of 92 pairs of con- 

 jugants (184 individuals). The larger individual of each pair is called a* the 

 smaller b. The unit of measurement is 4 microns (so that to obtain the lengths in 

 microns, the measurements given are to be multiplied by 4)- 



The mean size is 193.283 ± 0.475 microns; the standard devia- 

 tion 9.550 ± 0.336 microns (Shepard's correction being em- 

 ployed), and the coefficient of variation is 4.941 ± 0.174 per cent. 

 The important point, for present purposes, is the coefficient 

 of correlation in length between the two members (a and h) of 

 the pairs. This turns out, as computed from table 2, to be 0.3881 

 ± 0.0422. This signifies that if we select members having a cer- 

 tain length, when the length of these selected members (a) is 

 changed by one unit, the length of the mates h is on the average 

 likewise changed in the same direction, but that there is sufficient 

 variation so that the average change for these unselected mates 

 h is but 0.3881 of the change in the selected members a. 

 Now the question which interests us at present is this : 

 When we obtain progeny from the two members, a and 6, of 

 the pairs, will these progeny likewise show a similarity in size 

 and hence a coefficient of correlation? And will this similarity, 

 as measured by the coefficient, be less than that of the parents; 

 or equal to it; or greater than that of the parents? 



