154 H. H. NEWMAN 



All of the counts herewith presented have been systematically 

 repeated and checked over by a competent assistant, whose 

 services have very materially lightened the necessary drudgery 

 incident to this type of investigation. 



1. POLYEMBRYONIC CORRELATIONS IN THE BANDED REGION 



In the former paper dealing with this subject the interrelation- 

 ships of the individuals of a set of quadruplets were referred to as 

 fraternal or intra-fraternal correlations. The relation, however, 

 is not fraternal but one of a decidedly more intimate character, 

 and a special term is required to express it. For lack of a better 

 phrase I have chosen to refer to the general correlation within the 

 set of quadruplets as polyembryonic correlation. These relations 

 are unquestionably equivalent to intra-individual relations in 

 other forms and therefore should be determined before the 

 hereditary relations between parent and offspring are considered. 



In determining the coefficients of correlation for the polyem- 

 bryonic relation the simple method devised by Harris ('10) and 

 used in the earlier study will be adhered to. The method has the 

 advantage of obviating the necessity of plotting correlation tables. 

 One has merely to determine the mean, the square of the stand- 

 ard deviation (ax-) and the square of the positive differences 

 {(TV-), since positive and negative differences are equal where each 

 individual is treated as a subject and as a relative in computing 

 correlations. The formula used is as follows: 



= |l-l^| 



i 2aX^\ 



Then the probable error of the determination is derived by 

 the use of the usual formula : E^ = -' f-^ - 



For my own satisfaction I took the trouble to plot a regular 

 correlation table for the polyembryonic relation and found that 

 it required, even when small figures were used, a sheet of paper 

 2 feet square, and capable of reproduction only in the form of a 

 much folded chart, the value of which would scarcely warrant its 

 publication. 



