Chromosomes were studied in a mentally retarded boy with microcephaly, growth retardation, facial erythema, café-au-lait spots, and IgA deficiency. In the lymphocytes there was a remarkable tendency to exchange parts of the chromosomes Nos. 7 and 14, the translocations almost exclusively taking place in bands 7p13, 7q32 and 14q11. Seven different types of rearrangements between Nos. 7 and 14, and some other chromosomal aberrations were found. No abnormalities could be detected in the bone marrow. The patient somewhat resembles those affected with ataxia-telangiectasia or with Bloom's syndrome, but on clinical and cytogenetic grounds these disorders could be excluded. 7/14 Translocations similar to those found in our patient's lymphocytes have been reported to occur very rarely in the lymphocyte cultures of individuals with apparently normal chromosome constitution. A relationship between these phenomena may exist.

A balanced complex chromosome rearrangement (CCR) involving four chromosomes is very rare and may lead to different types of aneuploid germ cells. We report a liveborn child with multiple congenital anomalies and an apparently balanced translocation, t(11;12). High resolution chromosome analysis in the mother showed a CCR involving chromosomes 5, 11, 12, and 16. In situ hybridisation showed that this CCR was the result of a five break rearrangement, and that the derivative chromosome 12 consisted of parts of chromosomes 5, 11, and 12. From this it could be deduced that the karyotype of the child was not balanced, but resulted in partial trisomy for Sq and partial monosomy for 12p. The clinical findings in the child were compatible with partial trisomy for 5q.

This special issue brings together philosophical perspectives on the debate over cognitive ontology. We contextualize the papers in this issue by considering several different senses of the term "cognitive ontology" and linking those debates to traditional debates in philosophy of mind.