No. 3, December, 1920] GENETICS L53 



ness and of retinitis pigmentosa in Holland the following conclusions have been drawn by 

 the writer: A. Marriages of relal Lves gave three t imes as many cases of deafmuten mar- 



riages between non-relatives, if the number of marriages between relatives is taken as being 

 2 per cent of the total number of marriages; (B) If childless main re eliminated, deaf- 



muteness occurs among Protestants in 13.6 per cent, when both parents are deaf-and-dumb; 

 in 16.3 per cent when one of the parents is deaf-mute. For the Jews these numbers are 42.8 

 per cent and 33.3 per cent; for the Catholics in both cases per cent; C. Deaf-muteness is 

 found among Jews in 5.5 times as many cases as within the Christian inhabitant-: D. The 

 number of childless marriages is greater when both parents are deaf-mute and the number of 

 children fewer in marriages between two deaf-mutes, than in marriages between deaf-mute 

 and normal. True congenital deaf-mutes seem to be most frequent among the Jews. — For 

 retinitis pigmentosa the writer gives these conclusions: A. The male sex is more susceptible 

 than the female (relation 3:2), a fact already found by Nettleship; B. Out of the marriages 

 of retinitis-pigmentosa patients 14 per cent are childless; C. The abnormality is most found 

 among the Jews (6 times as many as might be expected), least among Catholics; D. Of all 

 patients 22 per cent are born from consanguineous marriages (also found by Leber and Nettle- 

 ship); E. Direct heredity could be confirmed in 25 per cent of the observed cases; F. Out of 

 167 patients of retinitis pigmentosa, 14 were also deaf-mutes; of these 14, 6 were born from 

 consanguineous matings; G. Retinitis and deafness combined were found in 24 cases, of which 

 7 descended from consanguineous parents; retinitis with deafness as family-character was 

 observed in 6 cases. — M. J. Sirks. 



1073. Dickel, F. Die geschlechtsbildungsweise bei der Honigbiene wie deren grund- 

 satzliche Bedeutung fur die Geschlechtsbildungs frage iiberhaupt. [The manner of sex deter- 

 mination in the honey bee and its fundamental significance for the problem of sex determination 

 in general.] Zeitschr. Wiss. Insektenbiol. 13: 33. 19 — . 



1074. Doyer, J. J. Th. Proeve van een onderzoek omtrent het familiair en hereditair voor- 

 komen van tuberculose volgens de wetenschappelijk-genealogische methode. [Preliminary 

 researches on the familial and hereditary occurrence of tuberculosis.] Diss. 214 p., 7 genea- 

 logical trees, and 258 quarter tables. J. B. Wolters: Groningen, 1920. — Author's medical prac- 

 tice has supplied to him a very extensive material for obtaining deeper insight in the relations 

 of hereditary dispositions and tuberculosis. The author's studies are not yet decisive as to 

 the question, whether differences in disposition may be inherited, but his provisional results 

 show unmistakingly a certain individual disposition for tuberculosis, that may go farther by 

 inheritance in succeeding generations. Seven genealogical trees and 256 quarter-tables 

 contain a rich material for his provisional hypothesis. — M. J . Sirks. 



1075. Elderton, Ethel M. Life-history albums. Biometrika 12: 373-374. Nov., 1919. 



1076. Frets, G. P. De polymerietheorie getoetst aan de erfelijkheid van den hoofdvorm. 

 [The theory of polymeric factors, tested by heredity of head-form in man.] Genetica 2: 115-136. 

 Mar., 1920. — The results obtained by the writer in measuring a great number of lengths and 

 breadths of human skulls, may be explained by accepting, according to the polymery-hypothe- 

 sis of Nilsson-Ehle, a number (at most 13) of like factors, working in the same direction. 

 These heritable factors may be identical. The important fact, that the amplitude of varia- 

 bility, shown by skull-measures of children, moves with the skull-measures of the parents, is 

 in perfect harmony with the polymery-hypothesis, the experiments of Nilsson-Ehle giving a 

 solid, though still narrow, basis for this hypothesis. Another explanation could be derived 

 from the hypothesis of selection, as in its new form defended by Castle. In author's opinion 

 however, the polymery-hypothesis has a greater degree of probability. — M. J. Sirks. 



1077. Frets, G. P. Over de erfelijkheid van den hoofdvorm. [Heredity of head-form in 

 man.] Handelingen Nederl. Natuur- en Geneeskundig Congres (1919) 17: 350-359. 1920. — 

 Brachycephalic as also dolichocephalic form of head are hereditary characters. Among brach- 

 ycephalics must be noted two classes, macrobrachycephalics and microbrachycephalics. 



