304 UNIVERSITY OF VIRGINIA PUBLICATIONS 



scheme. The second case is very much more damaging. Here a certain 

 sailor is said to have had seven left-handed brothers and six left-handed 

 sisters. His mother was left-handed, and had three left-handed brothers 

 and three left-handed sisters. The father was right-handed but had a 

 left-handed brother who had five left-handed children. The maternal 

 grandfather was also left-handed. This is a most remarkable family his- 

 tory! As given it undoubtedly indicates the dominance of left-handedness 

 in this stock. In the three fraternities of this family history given by 

 P6r6 total left-handedness seems to result from a right-hand-left-hand 

 cross. The case weakens somewhat, however, when we notice that in 

 neither case of the right-handed individuals is the ancestry known. But 

 even on the presumption that they are heterozygotes, the case for the last 

 generation, at least, is not materially improved. This fraternity can be 

 brought into line with Mendelian principles on the assumption that the 

 father was really a mild left-handed individual; or on the hypothesis 

 of reversed dominance. Cunningham,* also, believes very strongly in the 

 hereditary nature of left-handedness, but does not discuss its behavior in 

 crossing. 



In another set of one hundred and one pupils concerning whom no 

 further data were given, four are left-handed. 



In a colored school of Montego Bay, Jamaica, British West Indies, 

 among two hundred (200) pupils (ninety-four (94) females and one hundred 

 and six (106) males) there were six (6) left-handed females and five (5) 

 males. t The percentage, 5J, is slightly higher than among the colored 

 school children of the south, namely, about 4 per cent. ' Of these eleven 

 left-handed pupils seven had either a left-handed father or mother; the 

 other four had a close relative who was left-handed. 



Summarizing the data from the twelve of the foregoing pedigrees with 

 childships of more than four individuals, we see that there are twenty-one 

 (21) right-handed to nineteen (19) left-handed females, and nineteen (19) 

 right-handed to nine (9) left-handed males. In these fraternities the num- 

 ber of left-handed females is twice the number of left-handed males. The 

 number of left-handed is to the number of right-handed as twenty-eight 

 (28) is to forty (40), or as one to one and one-half. This is the identical 

 result of my earlier study. On the most legitimate assumption — in view of 

 the fact that the investigation is confined to left-handed fraternities — 

 that the parents are all heterozygous, the proportion does not accord with 



* Loc. cit. 



t These data were collected incidentally during a month's work at the temporary 

 Marine Biolog'.cal Laboratory of the Carnegie Institution of Washington, during 

 the spring of 1912. 



