168 

 I. 



The Journal of Heredity 



n. 



m. 



IV. 



6 





i i ■, Si 7 4 * W 17 /J /J 'V /^ /* /' " Tl T^ " ^' " " " " " " " " J' ^' 



VI. 



6 6 n 



<3 



6 cS© 



DESCENDAISTS OF DR. WI 



Dr. Little, a resident of Carlisle, England, and a descendant of the famous Percy family, emigrated to Ame: 

 hair, and has passed this on to a large number of his descendants. The above pedigree chart shows 1 

 that the individual was marked by the white lock of hair. For the sake of conciseness, large symbo 

 indicates the number of children in the fraternity, a smaller numeral above showing the number who w 

 matings has not been shown, since they were all with unaffected individuals. Thus when a parent hai 

 one not possessing it (recessive), or in genetic notation a DR mating, while when the symbol is white 

 between two who did not carry the trait; in such cases, the trait could never reappear in their descendan 



below the white lock of hair, a white 

 heart-shaped spot on the right knee 

 with a ribbon running down the leg and 

 encircling the ankle, and a white mark 

 on the abdomen." 



Lad (V. 59) now 12 years of age had 

 in his early childhood a patch of yel- 

 lowish hair on the back part of his head. 

 At this time, however, its color has 

 changed completely to that of the rest 

 of his hair. 



The accompanying chart represents 

 203 individuals of whom we have 

 accurate information. All are blood 

 related. Only one consanguineous mar- 

 riage has been contracted, that of a son 

 of III. 5 and the third daughter of III. 

 12. Both families of III. 5 and III. 12 

 are free of the mark and the four children 

 of the cousin marriage are also. 



An examination of the chart shows 

 that the white lock crops out only in 

 those families one parent of which is 

 thus marked. It is further seen that 

 the lock behaves as a simple dominant 

 with normality as recessive. Conse- 



quently two types of matings are 

 represented, i. e., DR x RR and RR x 

 RR, the individuals with the frontal 

 patch being hybrids (DR) and the 

 others (RR) pure recessives. Theoret- 

 ically we should expect to find the 

 leucotic spot in one-half of the children 

 in families where one parent is marked, 

 and not at all in children of unmarked 

 parents. These expectations are fairly 

 well borne out by the actual data which 

 give for the former 45 with, to 51 with- 

 out the "flare," and for the latter, none. 

 The above statements apply equally 

 well to the cases of Rizzoli, Hamian 

 and Cane. These pedigrees give the 

 ])roportions of those with, to those 

 without the albinic lock as 17 to 15, 

 23 to 15 and 23 to 13, respectively. 

 Combining the data at hand we obtain 

 the interesting result of 108 with the 

 white lock and 94 without. Thus the 

 conclusion seems warranted that the 

 white lock is a simple dominant and that 

 it follows closely the Mendelian law. 



