148 



FAMILY STUDIES IN BUILD. 



These series of progeny fluctuate in build around 36. It seems 

 probable that the variable progeny are the offspring of heterozygous 

 parents, but this can rarely be proved, since the build of the grand- 

 parents is not often available in the present series. 



That there are really at least two kinds of matings of the M X M 

 type is shown more conclusively by figure 50, in which two modes, 

 at 33 and 36, respectively, are clearly seen. The conclusion seems 

 to be justified that the mode at 33 is that of progeny derived from 

 the M biotype and the mode at 36 is that of the progeny of hetero- 

 zygous M parents. The existence of these two modes in figure 50 is 

 thus evidence of segregation. 



Additional evidence is found in other matings, likewise. Thus the 

 M X F mating shows two modes, at 33 and at 36 (fig. 51). There is 

 also one other, possibly significant, mode, namely, at 38, in the fleshy 

 group. Since F parents are sometimes homozygous, mating with M 

 would tend to produce medium-fleshy progeny (i. e., 36). The F 

 parents are, however, frequently heterozygous, containing both slen- 

 der, medium, fleshy, and even very fleshy gametes; and, accordingly, 

 we should expect somatic segregations at about the points 30, 33, 36, 

 and 38 as centers, just where we find them. 



Again, the S X M mating yields (fig. 52) modes at 32 and 35 

 respectively, a shade lower than those of the M X M or M X F 

 matings; but the male offspring (taken alone) gives modes at 33 and 



'26 28 30 32 34 36 38 40 42 44 46 48 50 52 54 56 

 Fig. 50. — Polygon of distribution of offspring of M X M matings (from Appendix table X) 

 for males, females, and sexes combined. Abscissae: index of build, English system. Ordi- 

 nates: absolute frequencies for males and females and their half sum for the sexes 

 combined. 



