Schultz: Zveodactylv 



117 



fingers (Roskoschny,^ Wolff, '^ or be- 

 tween the first and second, fourth and 

 fifth, or even between all the fingers 

 (Pfitzner).^ Such correlations between 

 web-formations of foot and hand are of 

 special interest and should always be 

 carefully searched for in future records 

 of zygodactyl toes. 



Webbing between the second and 

 third toes may occur only on one side 

 in all the affected members of a family, 

 as the family reported by Sommer,* in 

 which it appeared on the right foot 

 only; or the web may extend farther 

 on the right than on the left side, as in 

 the family recorded by Schofield, or 

 vice versa, as in the case of Hurlin. 

 Finally, zygodactyly of the foot is not 

 restricted to the male sex and therefore 

 is not a secondary sex character, as 

 assumed by Schofield; it has been ob- 

 served in a number of females as well. 

 The writer, for instance, found it in a 

 newborn girl, the zygodactyl feet of 

 which are shown in figure 9. 



The three charts given in this paper 

 were redrawn by the author from 

 reports found in the literature, showing 

 the inheritance of zygodactyly. The 

 original pedigrees were presented ac- 

 cording to widely different methods, 

 but in their present shape they will be 

 found easier for comparison with one 

 another and with the two charts 

 recently published in this journal. ^-^ 

 The following general conclusions in 



regard to the rules of heredity of 

 webbed toes can be drawn from the 

 pedigrees given herein, together with 

 those by Hurlin and Schofield. It 

 can be stated, first of all, that appar- 

 ently in no zygodactyl family does the 

 anomaly skip a generation; i.e., those 

 individuals who are free of the condi- 

 tion, although of zygodactyl strain, 

 will in all probability have only normal 

 children. Another striking feature is 

 the fact that the chance for the female 

 to transmit webbed toes to her chil- 

 dren is very much less than for the 

 male. However, since this does occur, 

 the conclusion by Castle^ based upon 

 the pedigree by Schofield, that webbed 

 toes have the distribution in heredity 

 of a Y-chromosome, is not borne out 

 by our material. It also seems that 

 female progeny is in general less apt to 

 inherit zygodactyly than male offspring. 

 How closely the condition is inherited is 

 shown by the number of families in 

 which an affected father transmits the 

 defect to all of his children (Fig. 13: in 

 all generations except where trans- 

 mitted by females; Fig. 11: generation 

 III and one generation, IV; Schofield: 

 one generation, IV). Only when more 

 pedigrees for zygodactyly have been 

 recorded will it become possible to 

 enlarge on these conclusions and at the 

 same time to place them on a firmer 

 basis. 



* Roskoschny, F. 1918. Symmetrische Syndactylie beider Hiinde und Fiisse. D. Mediz. 

 Wochenschr., vol. XLIV, p. 350. 



^ Wolff, F. 1918. Ein Fall dominanter Vererbung von Syndactylie. Archiv f. Rassen- u. 

 Gesellsch. biol., vol. XIII, pp. 74-75. 



^ Pfitzner, W. 1898. Beitrage zur Kenntnis der Missbildungen des menschlichen Extremita- 

 tenskelets. Morphol. Arbeiten, vol. VIII, pp. 304-340. 



* Sommer, 1916. Zur forensischen Beurteilung der Erblichkeit von morphologischen Abnor- 

 mitaten under der Papillarlinien der Finger. Arch. f. Kriminologie, vol. LXVII, pp. 161-174. 



' Castle, W. E. 1922. The Y-chromosome tvpe of sex-linked inheritance in man. Science, 

 vol. LV, pp. 703-704. 



