Pattern regulation in defect embryos of Xenopus laevis.

Defect embryos of 24 series were prepared by removing increasing numbers of blastomeres from an 8-cell embryo of Xenopus laevis. They were cultured and their development was examined macroscopically when controls reached a tailbud stage or later. Results show that most of defect embryos of 12 series develop normally, and some of them become normal frogs. Each of these defect embryos contain at least two animal blastomeres, one dorsal, and one ventral blastomere of the vegetal hemisphere. This suggests that a set of these four blastomeres of the three types is essential for complete pattern regulation.