Protein synthesis and germ plasm in cleavage embryos of Xenopus laevis.

(3H) leucine was injected into unfertilized eggs, fertilized eggs, and Stage 2-12 embryos of X. laevis. Incorporation of the leucine into protein by blastomeres containing germ plasm was studied autoradiographically. Eggs, both fertilized and unfertilized, actively synthesized protein, ad did embryos from Stage 2 onwards. Probably all blastomerers containing germ plasm were labelled. In embryos from Stages 4-12, the germ plasm itself was also labelled, and this result suggests that the germ plasm is metabolically active during cleavage.