[Cortical reaction in starred sturgeon eggs following fertilization and artificial activation]

An electron microscopical study of the fertilized sevryuga eggs has shown that 3 sec after insemination the most cortical granules in the region of the animal pole are already dehiscing and 10 to 30 sec the cortical granules release their contents under the membrane, but between the groups of cortical granules the contact of the cytoplasm with the membrane is still preserved. The full separation of the membrane observed under the light microscope at these times of fixation (San Felice fluid) is an artifact due to changes in the cortical cytoplasm properties. The rate of spreading of the cortical reaction over the egg surface is reduced from the animal pole to the vegetative one. By the criterion of the first changes discernible under the light microscope (formation of vacuoles and cytoplasmic threads between them) the maximal rate in the region of the animal pole amounts 360.5 mcm/sec and the average rate of the whole egg 46.5 mcm/sec; by the criterion of membrane separation the average rate amounts to 26.8 mcm/sec (at the temperature 21.9 degrees). The average rate of spreading of the cortical reaction in the sevryuga eggs is close to that in the sturgeon (Acipenser güldenstädti) and exceed ca. 3 times that in the sea urchin and teleostean eggs. The cortical reaction spreads at the same rate both in the fertilized and activated sevryuga eggs.