Here we report on two additional cases of distal 6q deletions with one case showing a terminal deletion of chromosome 6 (46,XY, del(6)(pter----q26:)) and one case showing an interstitial deletion of chromosome 6 (46,XY, del(6)(pter----q23::q25----qter)). The association of retinal abnormalities in 6q deletions is supported, and the additional manifestations of skin hyperextensibility, sacral abnormality, and imperforate anus are described.

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Summary The instrumentation and techniques developed for the investigation of fissure-flow in consolidated aquifers are described and illustrated by three case histories. The use of closed-circuit underwater television inspection of boreholes is outlined and consideration is given to the implications of flow rates by analyses of the tritium contents of some water samples.

A case of pseudoisochromosome 18q of prezygotic origin and a case of isodicentric chromosome 18 of postzygotic origin are presented to validate the differentiation between a true isochromosome and a pseudoisochromosome. This differentiation may be useful in elucidating the mechanism of the origin of an isochromosome.