36 MASS STUDIES IN BUILD. 



MASS STUDY OF VARIATION AND HEREDITY IN RUILD. 



Having considered the classification and something of the causes 

 of variation in build, we have now to consider the relation between 

 the build of the parents and that of the progeny. This is the mass 

 treatment of the data of "heredity" which was the prevailing method 

 25 years ago and earlier. It is still a useful method in the case of 

 traits due to multiple factors, such as the present one. 



The distribution of build in the children of the different matings 

 is given in tables 11, 11a, and 12. There are 15 possible different com- 

 binations of matings of the five grades. The first of these (VS X VS) 

 is not represented in our data, and the fifth, VS X VF, is represented 

 by only one mating and no column is devoted to it. The frequencies 

 are given separately for male and female offspring (table 11), and 

 again for both sexes together (table 12). Table 13 shows that there 

 is a considerable correlation between the average build of the parent- 

 age and that of the progeny. From the matings of the fleshier parents 

 the progeny are fleshier; from those of slender parents, slenderer. 

 This relation may conceivably be due to family tradition handed down 

 from parents to children. We shall see later that this hypothesis 

 meets with formidable difficulties to acceptance. The most reason- 

 able hypothesis is that there are, above all, hereditary family tend- 

 encies that help determine build. 



Comparing the tables for male and female offspring, it appears, 

 first, that there are, for some reason, more males than females about 

 whom data of build are given, probably because more males than 

 females know their stature and weight, or willingly record it ; second, 

 there are relatively more females than males of very slender build 

 (grades 22 to 31) ; there are recorded relatively more very fleshy males 

 than females (grades of 50 and above) ; third, there are relatively 

 more recorded daughters than sons derived from one very slender 

 parent, and from the F X F and M X M matings. The male progeny 

 are more variable than the female as 5.325 ± 0.084 is to 5.133 ± 0.089; 

 but the difference is less than three times the probable error, and is, 

 consequently, not very significant. 



Considering next the table of total progeny of the various matings, 

 it appears that the average number of children with recorded build 

 from the recorded matings is variable. In descending order the 

 fecundity of the matings is shown in table 14. This table shows that 

 larger families, on the average, were derived from fleshy parents than 

 from slender parents. Thus the F X F matings yield 2.3 times as 

 many children, on the average, per mating as the S X S matings. 



