the "Gray Crescent" in Sagittal Section
The figure below schematically depicts formation of the gray crescent of the Xenopus egg. The deep cytoplasm (yellow and blue) rotates with respect to the overlying cortex to produce a 30 degree relative rotation. Use the radio buttons at the right to toggle between the unfertilized oocyte's internal structure and that of the zygote following subcortical rotation. The following pages discuss the importance and mechanisms of rotation in Xenopus.