(1) Light and electron microscope observation of the mesoderm of the yold sac membrane indicate that individual presumptive precursors of the definitive-line are present as early as 2 days of incubation and give rise to sequestered populations of immature erythroblasts within sinusoids during the period of 2.5-6 days incubation.
(2) A pathway of the yold protein and factors determining its routing in the oocyte have been studied.
(3) W8 killed fowl and turkey embryos when injected into the yold sacs of embryonating eggs.
(4) Greatly elongated forms were commonly found in cultures and yold sac membranes after 5 to 7 days of growth but were only rarely seen in human lung.
(5) Lysolecithin-treated microsomal sediment and supernatant galactosyltransferase was inactivated by oleoyllysophosphatidic acid but not by palmitoyllysophosphatidic acid or egg yold lysophosphatidic acid.
(6) The excess 15N atom% (15N') was established in the crude protein, in the nitrogen from the TCE soluble and TCE precipitable fractions and in the N from 17 amino acids of the egg yold and egg white.
(7) The hematic yold precursor--vitellogenin--has been identified immunochemically in the serum of estrogenized females of the nest Triturus cristatus by employing an antiserum prepared against yold proteins.