First of all the Authors stress the importance of twin studies as a method of analysis of the pathological phenomena from a hereditary standpoint: to this aim, the Interzygotic Twin Method may be used in statistical studies, and the Clinical Twin Method in clinical ones. On this basis, the Authors report their observations, on a remarkable number of male twin pairs, affected by anomalies or syndromes including one or more genital dysfunctions, either in infancy or adolescence. Numerous cases of phimosis are thus presented, where the higher concordance in pairs of MZ twins stands for a hereditary conditioning; cases of hypospadias, showing a perfect symmetry of the malformation in the cotwins; cryptorchism, with various possibilities of presentation of the anomaly in the intrageminal comparison. The Authors also describe in detail, making an analytical intra-pair comparison of the symptoms and laboratory data, some cases of complex adiposogenital dystrophy, as well as one case of Laurence-Moon-Bardet-Biedl syndrome with different clinical manifestation in a DZ pair. The longitudinal study carried out over many years on some of the pairs affected by the above mentioned clinical pictures, and the clinico-statistical analysis of the cases under consideration allow the Authors to draw a number of positive conclusions concerning the variable, genotypic conditioning of the sex anomalies considered: in this field, as well as in many others of nosography, the Clinical Twin Method appears to be highly useful in practice, and unique by reason of its peculiarity.

A detailed description is given of the study performed in a pair of monozygotic Negro twins both suffering from hemophilia B; the bibliography is also reviewed about the occurrence of hemophilia in twins. The zygosity determination was performed utilizing anthropometric measurements, observation data, finger and palmar prints, seven systems of blood groups and five other genetic systems. The twins present a great similarity in the hemorrhagic symptoms, coagulation tests and Christmas factor level, but morphologic and physical differences due to the disease. These differences are explained by the diversity in the medical-hospital care which both received.

A female baby, showing the characteristic malformation pattern of the 17-18 trisomy syndrome, was found to have two extra chromosomes in groups 6-X-12 and 17-18, respectively: the presence of double drum-sticks and of double Barr bodies leads to interprete the karyologic finding as a triple-X + 17-18 trisomy. Autopsy showed an interventricular septal defect and an abnormal histological structure of the ovaries.

The Strong Vocational Blank inventory was administered to 43 pairs of identical and 34 pairs of fraternal twins in high schools in the Metropolitan Detroit area, and scores obtained on 44 vocational preference scales and 3 personality scales. F tests of the ratio between fraternal and identical within twin pair variances were significant beyond the .01 level of significance for the scales for Physicist, Mathematician and Osteopath while 9 more scales had F-ratios significant beyond the .05 level; these were for the scales of Dentist, Personnel Director, Veterinarian, Sales Manager, Aviator, Chemist, Public Administrator, Engineer and for the scale of Interest Maturity. Thus a total of 12 scales had F-ratios indicative of some hereditary contribution to the within pair variance of the twins in this study.

A comparison with the results published by Carter in 1932 was possible for 21 scales, by computing intraclass correlations for the present data. From these, as well as from the intraclass correlations reported by Carter, h2 values were computed and compared. There was stronger evidence for hereditary components in the earlier study, and the rank order correlation for the h2 values in the two studies was only .16, although in both studies it was found that the “Science” group of interest scales had the highest “average” h2 value (computed from average intraclass correlations, after Z-transformation).

These results are interpreted as indicative of a small but persistent contribution of hereditary components to the vocational choices reflected in scores on the Strong Vocational Preference Blank, particularly for scientific careers.

The use of the male form for the female twins in this study seems partly justified by the presence of equally often high mean values on scales and higher heritability estimates on some scales compared with the boys.

The Indian populations of the State of Santa Catarina, Brazil, are found in two places, Duque de Caxias and Xapecó. In the former live Aweikoma (possibly a Caingang subgroup), Caingang and Guarani; in the latter, Caingang and Guarani. The Aweikoma intercross freely with the Caingang, and the Aweikoma/Caingang group thus formed can be compared with the Caingang of Xapecó. The Guarani, on the other hand, are reproductively isolated from both populations. The Aweikoma/Caingang of Duque de Caxias and the Caingang of Xapecó differ from each other in characteristics related to racial composition (degree and amount of non-Indian genes), gene flow, average age of mothers and frequency of stillbirths. On the other hand, they show similarities in a series of demographic variables related to fertility, mortality and inbreeding levels. The index of total selection intensity is practically the same in the two localities.

Twin and pedigree data are presented which indicate that relative length of hallux and adjacent second toe is based on simple Mendelian genetic factors. The normal anatomical trait involves two alleles and a single autosomal locus. The factor for relatively long hallux is recessive to the one for relatively long second toe. There is no evidence of sex influence. Penetrance is 100%. Expressivity is variable, and bilateral discordance is observed in a minority of heterozygous subjects. In every such case, the dominant genotype is expressed in the right foot. The recessive and dominant phenotypes occur, respectively, in 76% and 24% of the greater Cleveland area Caucasian population. Gene frequencies in this population are 87% and 13%, respectively, for the recessive and dominant allele.

The plantar dermatoglyphic prints of 125 male and 125 female Panjabi Indians have been studied in order to determine the relative incidence of symmetry and asymmetry.

Females tend to possess a higher degree of symmetry than males. On the contrary, asymmetry shows a preponderence in males.

The differences between males and females are statistically significant when total symmetry is compared to total asymmetry, or when a comparison is made between the three groups of S and A. However, when the total symmetry and the rest of the combinations taken together are studied statistically, the differences appear to be of doubtful significance.