[Structure of the morphogenetic movements of gastrulation in Anura. I. Destabilization of ooplasmic segregation and cleavage under the action of clinostatic rotation].

The yolk segregation in the developing Rana temporaria egg was studied both in vivo and under the effect of clinostate rotation, i. e. slow rotation around the horizontal axis imitating the state of weightlessness. From the moment of fertilization and during the whole period of cleavage the yolk was shown to subdivide succesively in distinct phases which differ by the characteristic value of yolk granules. During the normal development, in spite of the marked variability of form and mutual position of phases, the main elements of their animal-vegetative order are preserved. Under the effect of clinostate rotation the process of normal segregation becomes destabilized and variations in the egg structure are expressed by the beginning of gastrulation in the diversity of variants of distribution of the cellular material competent to different morphogenetic movements.