Data for the Pvohlcm of Ecolidion in Man. 31 



/= 4-7- 



Thus, since the range of difference is from about - 10 to +10 inches, 

 w& have a fertility varying from 5*7 to about 3-7, or about 42 to 43 

 per cent, variation in fertility as we pass from wives relatively 10 inches 

 taller than their husbands to wives relatively 10 inches shorter ! In 

 other words, our homogamous influence is really cloaked by the fact 

 that big husbands and small wives have for extreme cases some 42 per 

 cent, less offspring than small husbands and big wives, a result of con- 

 siderable interest from the standpoint of genetic selection, and possibly 

 capable of easy physiological explanation, if pelvic measurements are 

 closely correlated with stature. 



In order to disentangle the two factors, I divided up my 205 pairs 

 into the quartile groups, and found the following results : — 



IX. 



Quartiles. 



Eange of difference. 



1 Total offspring. 



Mean size of 

 family. 



l&t 



-9-5" to - 2-25" 



1 



258 -5 



5-04±0-26 



2nd 



-.2-25" to 4 0-417" 



1 260-333 



5-08±0-26 



3rd 



+ to + 2-583" 



1 229 -083 



4 -47 ±0-26 



4tli 



+ 2-583" to +11 -0" 



i 215-083 



4 -20^0 -26 



The total number of offspring was 963, or the number to be expected 

 in each quartile 240-75, while the average size of the family is 4"6976, 

 with a standard deviation of 2-7826. These results show us that very 

 nearly half the marriages occur with the wife relatively taller than the 

 husband, and that such marriages give 54 per cent, of the total offspring 

 as against 46 per cent, produced wnen the husband is relatively taller 

 than the wife. The mean family with mother relatively taller than 

 father is 5-06±0'18, and that with father relatively taller than mother, 

 4-33 ±0-18, a difference which may be taken as significant. 



Grouping the 1st and 4th and the 2nd and 3rd quartiles together, 

 we have for the mean family Avhen husband and wife differ consider- 

 ably 4*62 ±0*18, and for the mean family when they differ but little 

 4-77 ±0-18. This difference in itself, however, unlike that recorded 

 by the previous process of investigation by weighting with fertility, 

 would hardly be sufficient to demonstrate a correlation between 

 fertility and homogamy. 



I accordingly made out a fourth correlation table, in which the vari- 

 ables tabulated were diff'erence of relative statures of husband and wife, 

 without regard to its sign and size of family. The mean relative 



