THE CHROMOSOMES AND ISOENZYMES IN MARGINAL POPULATIONS OF THE COMMON SHREW (SOREX-ARANEUS) IN THE VISTULA-DELTA

The chromosomes and isoenzymes of the common shrew populations in the Vistula dell:a were studied. Twenty nine out of 33 shrews were charact erised by the karyotype XX/XY(1)Y(2), af be, j/l, hi, g, k, in, n, 4 p , q, r, tu. We suggest that they be described as the Nogat race. The o ccasional occurrence of ko and gin metacentrics is the result of intro gression from the neighbouring races inhabiting adjacent areas. Of 22 loci scored, six appeared to be polymorphic. The studied area was homo genous with respect to protein variation. The hypothesis of the presen ce of a gentle dine of Pgm-3(B) allele frequency in the hybrid zone Dr uzno/Legucki Mlyn was not supported. The frequencies of esterase (Est- l) and mannosephosphate isomerase (Mpi) fit closely to the pattern of variation for Poland.