If subcortical rotation is crucial for subsequent axis formation in the amphibian embryos, then two things ought to be true: (1) perturbing the ability to undergo subcortical rotation ought to prevent correct axis specification, and (2) in such a "rotationally challenged" embryo, artificial rotation ought to be able to "rescue" the defects caused by prevention of normal rotation. In fact, methods have been devised to perform these two experiments.
Treatment of the vegetal hemisphere with ultraviolet light will prevent subcortical rotation. After UV treatment, zygotes can be embedded in ficoll or in agar on Petri plates. The embryos, whose cortices cannot move, are tilted (90 degreesfor > 30 min. works well), resulting in an artificial rotation. Click the highlighted ledgends to look at the results of these experiments.