156 H. H. NEWMAN 



2. Males as a sex would seem to show a greater absolute vari- 

 ability as attested by the higher standard deviation and the 

 greater actual differences among individuals of a set, but, rela- 

 tively to their standard deviation, their differences are small and 

 this makes males appear to be a little more closely correlated than 

 females. The difference is slight, though greater than the com- 

 bined probable errors, and may not be significant. Subsequent 

 determinations seem to contradict the earlier finding as to the 

 higher degree of variability of males as a sex. 



3. It may he considered as established that the coefficient of cor- 

 relation for the poly embryonic relation, as determined for the banded 

 region, is the equivalent of that determined for intra-individualistic 

 relations, and is of a totally different order from that shoivn to obtain 

 for any inter-individualistic relation previously ascertained. 



2. INTRA-PAIR CORRELATIONS IN THE BANDED REGION 



Relations even more intimate than those just presented, ob- 

 tain between the individuals of a pair. Since there are two pairs 

 in each set of quadruplets this intra-pair relation is an intra- 

 poly embryonic relation. The two individuals of a pair have been 

 shown to be derived from a common bud of early embryonic 

 tissue and to retain their paired relation through their placental 

 connections, one pair being attached to the right hand placental 

 disc and the other pair to the left. There can now be no doubt 

 that these placental relations serve as valid criteria of genetic 

 relationships within the set. We should then expect, a priori, a 

 higher degree of correlation between these 'twins' than obtains 

 for the quadruplets. 



In brief the calculation based on the data in table 1, A and B, 

 give the following results: 



a. Intra-pair correlation for 56 sets of male quadruplets is 

 0.9333 ± 0.0082 



b. Intra-pair correlation for 59 sets of female quadruplets is 

 0.9182 ± 0.0097 



No other pairing of individuals gives even so high a correlation 

 as that obtaining for the quadruplets, while for both males and 

 females it is plain that the intra-pair relation is more intimate 



