A sample of 122 twin pairs and 166 singletons from the urban Punjabi population of Chandigarh was studied. The observed frequency of double occipital hair whorls was higher in twins than in singletons (P < 0.01). The possible association between twinning and double occipital hair whorls is discussed.

In order to test if arm folding is a hereditary trait, 319 couples of parents and their 897 children have been examined. The distribution of the two phenotypes, D and G, is different from a O.5-0.5 distribution. No influence of sex nor age is observed. The matings are random and the mean number of children per family is the same for each type of mating.

The analysis of family data does not prove the hypothesis of a hereditary transmission of the trait, and important discrepancies are noted between observed values and those expected for genetic mechanisms with two alleles, D and G, of an autosomic or sex-linked gene.

Three familial cases of epibulbar dermoids, associated with lid ptosis, antimongoloid aspect of the palpebral fissure and nasal lobuloschisis are reported.

The hereditary character of this malformation is interpreted in terms of polimery.

A pair of female mongoloid twins was studied when they were ten years old and, again, some thirty years later. A careful comparison was made of the similarities and differences between them in features or traits which have proved to be useful in determining the zygosity of like-sexed twins.

Though some of these characters can be, and frequently are, considerably modified in the presence of mongolism and so lose part of their value for that purpose, the differences noted in these twins, both as children and as middle-aged adults, are thought to outweigh their similarities and so warrant the conclusion that they are, indeed, dizygotic.

Three pairs of male twins concordant for muscular dystrophy are presented. Two of these pairs are shown to be monozygotic and affected with the Duchenne form of muscular dystrophy. The third pair is probably dizygotic. The clinical and genetical features of each pair of twins are discussed. Pedigrees with photographs of the twins are presented.

Following a suggestion of Gedda and Bérard-Magistretti, intra-pair differences between MZ twins in fusional reserves were compared with differences in psychological variables. While the strong relationship between twin leadership and FR which these workers found in twin children was not confirmed in the present small sample of 14 adult pairs, the twin with the higher FR tended to be the more introverted, the more intelligent and the one who volunteered for the investigation. He also tended to be the taller and the first born.

Further studies, including the temporal reliability of scores of fusional convergence, are required before the value of this characteristic as a psychological criterion can be established.

The acute form of twin-to-twin transfusion syndrome is caused by rapid transfer of blood from one of the twins to another via placental anastomoses. Usually, this only occurs during the second stage of labour as a result of a sudden relative rise of blood pressure in one of the fetal circulations. This can result in the sudden intrauterine death of a fetus (or both, as in our case). Currently, there is no reliable means of identifying such an at-risk pregnancy by means of ultrasound antenatally. We would classify this as TTTS Type III.

A survey conducted at the Rehabilitation Institute of Montreal, covering 250 cases of cerebral palsy, came to include three pairs of identical twins, all discordant as to the disease. Pair I was female, 8 years old; Pair II, male, 6 years old; Pair III, female, 18 years old.

All vere subjected to physiatric, psyschiatric, and psychological tests as well as to tests involving activities of daily living. In each instance, the study was completed by EEG's still and motion pictures. The investigations included psychological and psychiatric evaluation of parents.

Extensive medical, psychological and psychiatric conclusions are drawn.

The Twin Clinical Method (Gedda, 1963) has been applied to the study of dental pathology. Four cases of MZ female twin pairs have been studied, concordantly affected by dental agenesis (case I), mirror-imaging dental agenesis (case II), diastema (case III), and dental caries and enamel dystrophy (case IV). The test has also been applied, and for the first time, to a set of MZ female triplets, concordantly affected by dental caries and malposition.

In all the above cases, the test has permitted to reject hypothesis of a concordance being due to chance, while postulating the existence of a causality.

The latter is ascribed to the common heredity characterizing MZ cotwins.

Almost one century after Galton's first scientific formulation of the Twin Method, based on the comparison of MZ and DZ twin series, not only twin studies play a fundamental role and the Interzygotic Test is widely applied in human and especially medical genetic research, but new methods have also been worked out, such as the Azygotic Test and the Twin Clinical Method.

Moreover, the study of twins has more recently led to new insights into the study of biological times, with the development of the modern branch of Chronogenetics.

The typical picture of mongolism has been observed in both members of a proved monozygotic twin-pair, aged 15. There is no indication in the family history of any hereditary predisposition, and both, the pregnancy and the birth were quite normal. The author reviews all cases previously reported, and expresses the opinion that mongolism is due to some phenomenon occurring during the germinating period, that is to say during the initial stages of development of the egg.

The genetical and medical importance of the research on the relations between blood groups and disease in the human populations requires a notable caution.

In the present paper the need is pointed out that the samples be representative, sufficient and homogeneous and some elements are noted which might introduce sampling biases.

Then the classic methods of analysis according to Aird, Woolf and Haldane are mentioned and their advantages and disadvantages outlined.

Finally a sequential method of analysis is presented that may be applied very easily and usefully by the researchers who might have the data directly and continuously in the hospitals.

È stato più volte segnalato che nelle fratrie di pazienti affette da disgenesia gonadica si verificano parti multipli in numero più elevato del normale. Nelle casistiche riportate (Boyer et al, 1961; Lindsten, 1963; Nance e Uchida, 1964), l'incidenza dei parti gemellari oscilla dal 25% al 63%; considerando globalmente tutti i casi degli autori citati (524 nascite), la frequenza risulta del 32%. Un'elevata incidenza di parti gemellari è segnalata anche fra ascendenti e collaterali delle pazienti.

Il fenomeno viene attribuito a fattori, probabilmente in parte ereditari, che possano provocare un'instabilità nei meccanismi che regolano le divisioni cellulari, tan to nella gametogenesi che nell'embriogenesi (Root et al, 1964). Si deve tuttavia segnalare che nelle fratrie dei pazienti con sindrome di Down, nonostante un errore meiotico nell'ovogenesi e l'età materna più elevata della media, non si osserva un numero di gemelli superiore al normale (∅ster, 1953; Allen e Baroff, 1955).

il quadro clinico e quello cariologico delle disgenesie gonadiche con fenotipo femminile sono alquanto variabili (Giusti et al, 1966). Si possono distinguere: (1) sindrome di Turner tipica, con bassa statura, quadro malformativo completo, compreso il tipico pterigium colli; (2) sindrome di Turner attenuata, con quadro malformativo attenuato, generalmente senza pterigium; (3) casi senza alcuna malformazione, eccettuata la bassa statura; (4) casi con disgenesia gonadica pura che presentano un aspetto somatico completamente regolare, salvo Pinfantilismo. Nella sindrome di Turner tipica il cariogramma rivela quasi sempre il caratteristico ipoploidismo XO; nei casi di disgenesia gonadica pura il cariotipo è molto spesso normale; negli altri casi il quadro è variabile: fra i soggetti con mosaicismo di tipo XO/XX prevalgono quadri di sindrome di Turner attenuata; fra quelli di tipo XO/XY sono abbastanza frequenti le neoplasie gonadiche del tipo del gonadoblastoma.

The so-called endogenous psychoses, i. e. the manic-depressive pychosis and the schizophrenias have still to be treated like functional characters, as their probably existing somatic bases are still unknown. It may be granted that these two groups are genetically different, though there are — particularly in isolates — hereditary types of psychoses mixed with both manic-depressive and schizophrenic symptoms. According to the data of twin research, schizophrenias and cyclic psychoses have no common genetic background.

The very high concordance of monozygotic twins for schizophrenia is liable to prove the high importance of genetic factors, while it does not exclude accessorial environmental influences in its etiology.

A simple recessive inheritance, which seemed to be outruled by most authors, appears now to be possible according to Garrone (1962). Other authors (Slater, Böök) pleaded for irregular dominance of major genes with or without single accessory genes, and others even for an unspecific polygenic origin.

The term “ schizoid ” is vague and does not correspond to a satisfactorily clear conception either clinically or genetically. It may be the incomplete expression of a disposition to schizophrenia and more often that of a recessive gene in heterozygotic state or an incompletely dominant gene. Schizoid features which have been observed twice in children with trisomy-22 are not likely to have anything to do with schizophrenic psychoses.

Most probably the schizophrenias are heterogenic, but not with regard to clinical variations such as hebephrenia, catatonia, dementia simplex or paranoides. At any rate, we should not rely too much on the empirical hereditary prognosis.

The study of the occurrence of schizophrenia in isolates has the advantage that we have to do mostly with one and the same biotype and that we are able to trace the presumable genes throughout 8 and more generations. On the other hand the number of character-bearers is numerically limited.

In an isolate of eastern Switzerland with about 400 individuals of a highly inbred and fertile population, the frequency of schizophrenia is at least 1.75%. There are accumulations of the trait in some families and collateral lines. The oldest cases of presumable schizophrenics go back a hundred years; the more recent ones were or are interned in the two Cantonal asylums. The diagnoses in their records were controlled by prominent Swiss psychiatrists. Among the parents and sibs of those schizophrenics only a few can be judged as “ schizoid ” at a psychopathic degree.

The parental consanguinity of our propositi is about three times higher than the average of this population, which also contains 3.5% of undifferentiated oligophrenia being low-grade in 1%. The frequency of both schizophrenia and oligophrenia does not account at all for the relatively high number of 5 so-called “ Pfropf-schizophrenias ” (i. e., combinations of schizophrenias with inborn mental deficiency); however, Larsson and Sjögren found the same in a Swedish isolate.

While the 14 cases of sure or most probable schizophrenia in our isolate do not clearly show a monomeric recessive inheritance (since Weinberg's sibmethod gives a =10.4% and Bernstein's a priori-method a P = 3.0%), the undifferentiated oligophrenia of all degrees most probably depends on one specific simple recessive gene. It is not unlikely after all that the schizophrenias be inherited in the same way in this population, provided there is a considerably reduced manifestation of a mutated autosomal gene.

In a pair of 14 year old DZ twins of different sexes, a particularly profound emotional separation becomes manifest during childhood.

The twins come from a family whose members are considerably introvert, and where very few exchanges of emotional manifestations take place. The male twin offers a more fundamental alteration of personality, and his emotional control is often overwhelmed by antisocial tendencies of relative frequency. In accordance with her family surroundings his twin, instead, possesses a particularly rigid and severe moral conscience.

The twins are spiritually separated when at the age of eight and nine years, the boy attempts certain sexual approaches on the little girl. At first the child consents, but gradually a most intense feeling of guilt rises up in her, which is accompanied by an aversion, rapidly changing into invincibile hatred towards her brother, whom she fears will subject her to further sexual practises.

Notwithstanding the preponderance of the sexual factor, the antisocial behaviour of the boy, also contributed to a certain extent to this separation.

From a psychoanalytic point of view, the girl's behaviour, characterised by a typical inversion of feelings could be in- terpreted as a reaction formation.

As the boy has been classified from a psychiatric diagnosis as bearing a psychopathic personality which occupies a position between neurosis and psychosis, the eventual possibility of a certain degree of familiar and social adjustement is not to be excluded.