The karyotypes of 39 avian species new to cytology are described, viz.

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The frequency of triploidy was studied in early chicken embryos and hatchlings and in adult chickens which showed symptoms of intersexuality at an early age. The incidence of triploid embryos in the strain involved was not very high (0.6%), but it appeared to increase significantly when embryos were studied from eggs laid by very young hens (4.4%). Among the hatchlings screened only one single triploid individual was found (0.2%). The majority of the adults suspected of intersexuality proved to be triploid with a ZZW sex-chromosome triplet (66.1%). These data are briefly compared to those available from the literature.

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