A case of one twin pair concordant or discordant as to a given disease is always very important for Clinical Genetics, especially when it is monozygotic. In Clinical Genetics, isolated pairs occur to the physician, and the diagnosis must therefore be based on intra-pair comparison. The statistical treatment of the case must consider the fact that a concordant monozygotic twin pair represents a statistical universe rather than a statistical unit. This entails taking into account many traits concerning the time of onset, the symptoms, development, result of treatment, etc. Suggestions are made for the statistical treatment of such cases.

The Authors report on a pair of MZ twins, only one of which affected by the Duchenne-type myopathy. Monozygosity is supported by the success of a reciprocal skin-graft.

Various hypotheses are discussed, including that of a somatic mutation during the first division of the egge producing the twins.

A study is described in which the spectral similarities in the voices of monozygotic, dizygotic and non-twin controls is compared. The results are based on a statistical comparison of the differences between pairs of individuals at a number of spectral points. The data are interpreted as showing that monozygotic twins are more similar in the higher but not the lower spectral ranges. It is suggested that the lower frequencies are more sensitive to transitory factors while the higher frequencies are more likely to reflect anatomic similarity.

A sibship is described showing partial aplasias of lower and upper limbs. The concordance of the malformations in the two brothers, the presence in the ascendents of various skeletal and extra-skeletal anomalies, as well as the lack of other causes which could have originated the malformations have made us diagnose the genetic origin of the malformation.

The authors report a case of regional ileitis (Crohn's disease) with an almost identical course in monozygotic twins. Monozygosity is determined by examination of many physical and serological characters.

Using Bansal & Rife's recent study (1962) as a working model, certain two-fold groupings of four palmar main lines and the axial triradii positioning have been proposed on the basis of the writer's unpublished work (1962). Some fairly encouraging penetrance figures suggest to apply the same groupings on twin data, on largest and richer family material drawn from the same Mendelian population, and to use other available methods of penetrance calculus, including one from concordance figures that is under investigation by the author.

The only case of so far known Tcheck quintuplets is reported, viz. two males and three females born in Moravia in 1780 and dead 24 hours after birth.

The Author analyses the family factors and also discusses about the validity of Hellin's law for multiple births.