[Mosaic (Chimeric) animals: their experimental production and application (author's transl)].

A method introduced by Tarkowski permits the aggregation (mosaic-like fusion) of mammalian eggs in the early stages of division. In this paper, a modification of the Tarkowski method designed to create multiparental (mostly quadriparental) chimeric mice is discussed. The method described is simple, more practical and time-saving. The problems in analysing clonal processes of development in mammals and the mechanisms connected with sex differentiation and tumour development are discussed.