The video sequence at the right was kindly provided by Dr. M.
Danilchik,
Univ. of Oregon Health Sciences Center. It shows how germ plasm becomes asymmetrically
distributed as a result of subcortical
rotation movements of the fertilized Xenopus egg. The germ
plasm is the brightly colored region of the vegetal cytoplasm
that becomes segregated to specific blastomeres
by the four-cell stage. The stain used here detects mitochondrial, which
are found at much higher density in the germ plasms of many organisms,
including worms, flies, and frogs.