Article révisé par les pairs
Résumé : Treatment of the sperm with U.V. radiation before the fertilization of the frog's egg leads to a typical haploid development, due to the early and complete elimination of the irradiated chromatin. On the other hand, if the sperms are treated with a nitrogen mustard, the development is quickly lethal: very unequal synthesis of DNA occurs in the two halves of some of the nuclei during late cleavage and early gastrulation; finally, embryos with highly unbalanced chromosomial sets (aneuploids) are obtained. © 1953 Verlag Birkhäuser AG.