72 HEREDITY AND EUGENICS 



as a simple Mendelian recessive character, at least in 

 some families. Ramale}^ (191 3) came to the same 

 conclusion, based on 1,740 cases. He estimated that 

 the condition is carried in about one-sixth of the 

 population. Left-handedness, as a character, may 

 bear some resemblance to reversed symmetry in 

 certain Gastropods. This reversal has been shown 

 by Conklin to begin in development with the cleavage 

 of the ^%%, the spiral cleavage being dextral in one 

 case and sinistral in the other, but its inheritance is 

 unknown. Ambidextrous individuals in man appear 

 to have inherited left - handedness and acquired 

 dexterity with the right hand. There are apparent 

 exceptions, how^ever (see Compton, 191 2, where a 

 number of references will be found), as in a family 

 quoted by D. J. Cunningham in the Journal of the 

 Anthropological Institute, xxxii., 1902, from Aime 

 Pere, where a left-handed mother and a right-handed 

 father had eight sons and six daughters, all left- 

 handed. If the father were heterozygous, this result 

 would be possible, though very improbable, even if 

 left-handedness were regarded as a recessive. It 

 would seem more probable that in such a case the 

 dominance has been reversed. There is also clear 

 evidence that in certain families the condition is 

 sex-linked. 



A recent paper by Beeley (1920) considers left- 

 handedness from various points of view, and gives 

 a number of references to the literature of the subject. 

 Estimates of the frequency of left-handedness have 

 varied between 6 and 2 per cent., wdth 4 per cent, 

 as the medium frequency. This applies to American 

 Indians (Apaches and Pimas), as well as to white 

 races. That the condition is more frequent in man 

 than in woman has been affirmed and denied. Some 

 have found it more frequent among delinquents and 

 among negroes, but there seems to be no sufficient 



