Pronunciation:SPI-r’l KLE-vegh

Etymology: The phrase, spiral cleavage, comes from two very different sources. Spiral is from the Greek to mean the coil or twist of a snake (speira, σπείρα). Cleavage is from the Old English cleofan, which means to split.

Spiral cleavage is typical of the Protostomata and is characterized by the division planes of early cytokinesis products of the zygote being oblique to the plane of the polar axis. This produces unequal cells in the developing blastula. Usually spiral cleavage is determinant.