Embryology of dolphins. Staging and ageing of embryos and fetuses of some cetaceans.

Comparative embryology has been neglected in the past decades. In our opinion the decreased interest has been caused by the fact that the time factor has not sufficiently been respected. Therefore we used the Staging and Ageing Method (Stĕrba 1999) to determine the ontogenetic age of embryos and to state the time tables and time relations of various ontogenetic events.

Sex chromosome abnormalities in natural populations of the common vole (Microtus arvalis).

Four specimens with an aberrant sex chromosome constitution were found in natural populations of the common vole (Microtus arvalis). Two females had an X0 sex chromosome constitution and single males were 2n = 47, XXY and 2n = 47, XYY, respectively. No apparent phenotypical anomalies were recorded in the sex chromosome aneuploids, but their fertility may have been impaired.