Effect of Thiourea on Development of the Sea Urchin Arbacia Punctulata

Sea urchin eggs which were subjected to varying concentrations of thiourea showed a number of pronounced effects. Concentrations of 1% or more resulted in a complete inhibition of cleavage. In 0.5% solutions of thiourea, the eggs developed normally until the blastula stage was reached. For as long as 72 hours, the eggs did not differentiate beyond the gas-trula stage. When the arrested gastrulae were returned to sea water, the inhibitory effects were reversible.