[The organization of the cortical layer of amphibian ova. 1. The ultrastructure of the cortex of the oocytes and ova of the clawed toad: the effect of divalent cations].

Ultrastructure of oocyte and egg cortical layer isolated in media containing various ions has been studied. The following results were obtained: 1) in cortical layer a two-component cytoskeletal system is present; morphology of this system changes during development; 2) cytoskeleton of the egg cortex acts as a two-component system in response to the influence of Ca2+: the cortex per se is destroyed while subcortex is contracted; 3) cytoskeleton of the oocyte cortex is destroyed under the influence of Ca2+; 4) nature and sensitivity to the absence of Mg2+ in the medium varies for cytoskeletal structures of oocyte and egg cortex.