Radial cleavage also known as merotrichousis the process of embryonic development in which the division of the zygote occurs along planes that are perpendicular to the animal-vegetal axis. This results in the formation of a stack of cells, each of which is called a blastomere. Radial cleavage is typically seen in embryos of deuterostomes, such as echinoderms and vertebrates.

In radial cleavage, the first division of the zygote occurs along the animal-vegetal axis, resulting in the formation of two blastomeres: the animal blastomere and the vegetal blastomere. The second division occurs perpendicular to the first, resulting in the formation of four blastomeres: two animal blastomeres and two vegetal blastomeres. This pattern of division continues, with each subsequent division occurring perpendicular to the previous division, until a stack of blastomeres is formed.

The pattern of radial cleavage is important for the development of the embryo because it determines the location of the different germ layers. The animal blastomeres will give rise to the ectoderm, while the vegetal blastomeres will give rise to the endoderm and mesoderm.