Acceleration of the Cleavage in Sea Urchin Eggs by Treatmentswith Local Anesthetics (I) Procaine Treatment*

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Abstract
Unfertilized sea urchin eggs were pre‐treated with 2–10 mM procaine sea water for 10 min and then fertilized 5 min later. These eggs hatched about 1–1.5 hr earlier than the control eggs. This acceleration of hatching seems to be the result of a reduction in the individual cleavage cycles.In the second series of experiments, eggs were inseminated at 5, 30 and 60 min after the procaine treatments. In this case, the rate of accelerated cleavage decreased gradually, as the intervals between the treatments and insemination were extended.Next, the minimum time‐length of procaine treatment to accelerate cleavage was determined. When eggs were immersed in procaine for 1 min, cleavage was accelerated as in the case of 10 min‐treatment, although acceleration to the same degree required higher concentrations of procaine solution.When fertilized eggs were post‐treated with procaine, cleavage was also accelerated, but both the rate of acceleration and the effective concentrations decreased with time after fertilization.