Chromosomes sexuels géants chez un Campagnol,Microtus agrestis L
In the vole,Microtus agrestis L., there are 46 chromosomes as in the twin-species,M. arvalisPallas. In striking contrast to this last animal, the sexual chromosomes, studied in the last spermatogonial divisions, are of gigantic size (X metacentric = 8–9 µ;Y acrocentric = 5–6 µ). The identification of theX is proved by the analysis of marrow-smears of the female. It is expected that several problems concerning the mode of attachment and the type of association betweenX andY can be resolved by the study of that most interesting rodent.