Protein-synthesizing activity of the anucleate polar lobe of the mud snail Ilyanassa obsoleta.

Polar lobes of eggs of the mud snail Ilyanassa obsoleta, detached at the "trefoil" stage of the first cleavage, are capable of incorporating labeled amino acid into protein. The rate of incorporation per unit volume is about half that of the whole egg. The ability to incorporate at a similar rate persists for at least 24 hours after isolation. The sum of the incorporation of isolated lobes and lobeless fragments approximates that of the whole egg. The results extend to this material (the anucleate polar lobe) evidence for long-lived messenger RNA. They suggest also that the demonstrated morphogenetic influence of the lobe, which is exerted primarily during cleavage, may be correlated with its ability to synthesize protein.