184 THE MICHIGAN ACADEMY ( )F SCIENCE. 



A STATISTICAL STUDY OF CONJUGATION IN. PAEAMECIUM. 



RAYMOND PEARL AND MARY J. BURR. 



(Abstract.) 



Professor Karl Pearson and his associates have demonstrated that 

 there exists in man a significant and measurable degree of assortative 

 mating. This assortative mating is of two kinds, (a) preferential mat- 

 ing, and (b) homogamy. In homogamy there is a tendency for a class 

 of males having a given character to unite with a class of females of a 

 generally like character. This results in a positive correlation between 

 the members of mated pairs with reference to the character under 

 consideration. 



From his family measurement data Pearson* has found the following 

 values for the coefficients of correlation measuring homogamy in man. 

 These values measure the degree of correlation between husband and 

 wife with respect to the characters enumerated. 



Stature 2804 ) 



Span urn - 1.000 pairs. 



Left fore arm , 1977 ) 



Mean 2257 



With reference to the character "duration of life" co-operative workf 

 in Pearson's laboratory at University College has shown that the mean 

 correlation between husband and wife is .22.33. In general the intensity 

 of homogamy in man, so far as it has been investigated, may be con- 

 sidered to be fairly represented by a coefficient of correlation of from 

 .22 to .23. This tendency of like to mate with like may be due either to 

 ''real conscious or unconscious assortative mating in man" or to indi- 

 viduals mating Avithin local sub-races where, on account of the similarity 

 of the environmental effects upon all individuals, there is little differ- 

 entiation. If it be due to this latter cause, random mating would, of 

 course, give a coefficient of correlation of approximately the same magni- 

 tude as that actually observed. That there is real assortative mating 

 with reference to the character "duration of life" Avas demonstrated by 

 observing that when male and female records were paired together at 

 random the resulting coefficient of correlation differed from zero by less 

 than half its probable error. Since, then, the observed positive correla- 

 tion between husband and wife is not a mere chance result, the assorta- 

 tive mating- thus demonstrated must be due either to conscious choice 

 or to some unknown non-conscious factor. 



The present work was undertaken with the view of determining whether 

 there is any tendency toward homogamic ])airing in an organism where 

 conscious choice can presumably play no part, and where we have the 



*Biometrika, Vol. If, p. 373. 

 tBiometrika, Vol. II, p. 481-498. 



