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A true hermaphrodite rabbit served several females and sired more than 250 young of both sexes. In the next breeding season the rabbit, which was housed in isolation, became pregnant and delivered seven healthy young of both sexes. It was kept in isolation and when autopsied was again pregnant and demonstrated two functional ovaries and two infertile testes. A chromosome preparation revealed a diploid number of autosomes and two sex chromosomes of uncertain configuration.

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The cause of masculinisation of the left ovary and the outgrowth of the vestigial right gonad was investigated in intersexual hens. Tumour-like cell masses, resembling mouse tubular adenomas of the ovary, were observed in the majority of masculinised left gonads. Except for one male and two intersexuals, testosterone concentrations were below detectable levels. For oestrogen, progesterone and the oestrogen : progesterone ratio all differences were significant, except for the difference between the intersex and the male. Histochemically this cell mass showed weak androgen-synthesising activity. These intersexual gonads showed similarities to normal testicular tissue. Karyotyping revealed 3n-autosomes and a ZZW sex chromosome constitution. The early and almost complete absence of cortical follicular structures was most notable and may have been the cause of the sex reversal.

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The G- and Q-bands and the location of the nucleolar organizer regions (NOR) in the chromosomes of Presbytis obscurus and the Q- and C-bands of P. cristatus pyrrhus are described. Their chromosomes are compared to those of Macaca mulatta and to other Cercopithecidae and Hylobatidae. The origin of the two different banding patterns of pair no. 1 in our specimen of P. cristatus pyrrhus is discussed.

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A number of cases of intersexuality occurred in a fairly large number of cases in 6-8 months-old laying hens on two poultry farms in the province of Limburg. When macroscopic and microscopic studies failed to supply any evidence concerning the cause of the considerable development of the right gonad, it was decided to do a chromosome analysis. Three intersexes in which the chromosomes were studied, were found to be triploid birds showing a ZZW sex chromosome combination, which aberration may have been the cause of the intersexuality observed.

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Somatic karyotypes of 13 species of ciconiiform birds, Phoenicopterus ruber chilensis, Phoeniconaias minor, Cochlearius cochlearius, Geronticus eremita, Threskiornis molucca, T. spinicollis, Balaeniceps rex, Ciconia ciconia, C. nigra, Euxenura maguari, Xenorhynchus asiaticus, Ephippiorhynchus senegalensis, and Leptoptilos crumeniferus are presented. The chromosomes of eight of these species are described in detail for the first time. Of special interest are a case of structural heterozygosity in a male B. rex and remarkably low diploid numbers in C. nigra (2n = ca 52) and L. crumeniferus (2n = ca 52). The karyological relationships of the ciconiiform families are discussed. The karyotypes of the Phoenicopteridae are identical to karyotypes found in various other bird orders. All members of the Ardeidae hitherto studied are characterized by a submetacentric third pair of macrochromosomes (subtelocentric in all other Ciconiiformes). All Threskiornithidae share a pair of acrocentric chromosomes resulting from a reciprocal translocation between a pair of microchromosomes and pair No. 1. Both the Ciconiidae and the Balaenicipitidae show the original structure of Nos. 1, 2 and 3, also found in the Phoenicopteridae and many other birds. In contrast to the Phoenicopteridae, however, both families share a relatively high number of medium-sized to small biarmed chromosomes with the Ardeidae and the Threskiornithidae. Several characteristics in this group of chromosomes separate Balaenicipitidae from Ciconiidae.

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The extensive literature on the origin of the ratites focuses mainly on three questions: are the ratites mono- or polyphyletic, did they evolve from flying ancestors, and are they primitive or advanced? Opinion tends to accept a common descent from flying ancestors for the large ratites (for a summary of ideas see ref. 1). They would have evolved on Gondwanaland some time in the Cretaceous and have become dispersed over the southern continents after its fragmentation. However, the position of the small New Zealand kiwis, in many respects the most pecular of all birds, is still a matter for conjecture. The chromosome complements of the large ratites have been found to be remarkably uniform. The chromosome set of the kiwi, described here, clearly links up with these, which may be recorded as another indication for monophyly of all ratites. It also indicates that we are dealing here with very ancient karyotypes.

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Chromosome studies in 4 families of Falconiformes, Cathartidae, Falconidae, Sagittariidae and Accipitridae showed that the karyological variety in this order is much wider than in any other avian order, which underlines the heterogeneous character of the group. Of the 4 families only the Cathartidae show karyological similarities with other avian groups (Gruiformes, Ciconiiformes), while the karyotypes of the Accipitridae are most uncommon among birds, because of the presence of only 8 microchromosomes.

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A detailed description is given of the somatic chromosomes of two specimens of Pithecia pithecia pithecia. An indiogram, constructed on the basis of metrical chromosome data, is presented and compared with those of two other members of the Pitheciinae. The possible karyological relationship with the Pitheciinae, and the cytotaxonomic position of this group within the Platyrrhini are briefly discussed.

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