[Induction of triploidy and the development of triploid mouse embryos]

By subjecting A strain eggs at the time of fertilization and polar body extrusion to 5 micrograms ml cytochalasin B digynic triploidy was produced in 80% fertilized eggs. 50% tripronuceate eggs developed into regular morulae and blastocysts with 2/3 the cell number of control diploids. Tripronuceate eggs were transplanted to recipients and examined between 9-11 th day of pregnancy. Development of triploid embryos up to 7 day is normal and most embryos form egg-cylinder. At 8 day embryonic part of the cylinders is underdeveloped and in latter development fails to form an embryo. Development of foetal membranes is much less affected and in successfully developing egg-cylinders their formation can be fully accomplished. Failure of embryonic development appears to be due to lower proliferation rate triploid cells than diploid, subnormal activity primitive streak, resulting, in shortage of mesoderm.