[Provocation of situs inversus by means of material defects in the lateral ectoderm of the gastrula ofTriturus alpestris].

Roundish pieces were removed from the lateral polar region of young gastrulae ofTriturus alpestris. These consisted mainly of undetermined ectoderm and partly of ventral mesoderm. The majority developed into normal embryos or embryos with minor abnormalities.After injury of the left side (101 cases) the gut situs of the larvae was normal in 85.2% median in 6.9% and inverted in 7.9%. When injured on the right side (106 cases), the larval gut situs was regular in 79,2%, median in 8.5% and inverted in 12.3%.These results support the statements of v.KRAFT (1968b) who also found a higher rate of situs inversus after irridiation of the right side. In contrast, defects on the left side are more effective in other regions and different stages of the embryo. The higher sensitivity for defects of the left side in the organizer region (v.WOELLWARTH, 1950) could be confirmed.