Biometrical genetical techniques have been applied to the analysis of certain anthropometric characters measured in 134 pairs of adult twins. After allowing for assortative mating it appears that there is a family environment (E2) component for variation in height larger than previously reported. “Fatness” traits – weight, ponderal index, and skinfold thickness – all show higher heritabilities in males and substantial E2 components in females, and reasons for this are discussed. The same is true for cephalic index and forearm length but the reason for these differences is not so obvious. Head length shows a much higher heritability than head breadth. A larger sample of DZ opposite-sex pairs would allow more powerful discrimination, but the variety of patterns of variation revealed by the model-fitting approach used here justify its use over more traditional techniques.

The inheritance of General Neurotic, Obsessive, and Impulsive Hysterical personality traits has been studied in a sample of 260 female and male adult same-sexed twins. At least one of the twins in each pair had been treated for neurotic or borderline disorders. The results showed that the General neurotic and the obsessive personality factor had a significantly but moderately high hereditary component. The same was also true for more than half of the 17 separate personality scales. No personality scales emerged as highly hereditary. Therefore, each item was analyzed separately, and items classified as either distinctly hereditary or environmental were placed in each of these two groups. The items of the two groups were separately factor-analyzed, and three hereditary and three environmental main factors emerged. The hereditary factors seemed to represent a basic core in the three personality factors of the total questionnaire, whereas the environmental factors could be explained as derivatives of early representation of the basic hereditary core, influenced by familial and cultural patterns.

Fifteen hundred palmar prints of normal persons and patients suffering from various diseases were studied and classified as to dermal ridge configurations at the base of digit IV, after the exclusion of main line C courses with endings at one of the palmar marginal regions. This classification scheme, based on the three classical reduction forms of line C (O,X(8),x), resulted in the differentiation of three main groups, A, B, and C. Within these main groups, pattern types with strong similarity were combined to subgroups allowing an easier documentation. Twin and family data were used to test whether the described pattern types, besides the classical abortive states O,X and x of line C (called special and intermediate forms), are heritable and for which of them a remarkable reduction tendency could be established. The results allow us to confirm the main grouping and the assumed reduction tendency of the special forms of group A.

Stillbirth rates of MZ and DZ twins in Japan gradually decreased during the period 1960–1967 and in 1974. The stillbirth rates of MZ and DZ twins were 0.270 and 0.224 in 1960, respectively, whereas the corresponding figures in 1974 were 0.135 and 0.099. The stillbirth rate was higher in MZ than DZ twins, in males than females, and in the second- than in the first-born. In both zygosities, the rates were higher in the first birth order than in the second, and then increased with birth order except in the sixth birth or more for MZ twins and for DZ twins born to mothers aged 35–39 years. The shorter the gestational age, the higher the stillbirth rate in both MZ and DZ twins, as expected. Mean gestational age was slightly shorter in MZ than in DZ twins. The decrease of the stillbirth rates can be explained partly by the reduction of twins with higher birth order, where high stillbirth rates of MZ and DZ twins are seen, and the reduction of older mothers.

Neither the percentage in the previous use of contraceptive pills nor the distribution of the time interval between the discontinuation of the pill and conception has shown any significant difference in twins and control singletons. Twin conception within one month after discontinuation of the norethynodrel type pill, however, was significantly more frequent, whereas after the use of the linestrenol type, it was lower.

Perinatal mortality in twins is found to vary widely in six developed countries for which national data are available. The influence of factors such as birth weight, maternal age, and parity is examined, but no consistent trend is found.

The case presented here may be the first report of symbrachydactyly in one child of monozygotic twins. Detailed testing of blood groups was performed to confirm zygosity. This case suggests that symbrachydactyly may be caused by intrauterine environmental factors.