1. The nature and behavior of the conjugated proteins in the hemolymph of adult female Periplaneta americana (L.) have been studied in relation to the ovarian cycle, using disc electrophoresis in polyacrylamide gel and various staining procedures. It is shown that there may be not only a change in the relative concentration of the different protein fractions with oocyte growth, but also differences in their chemical composition. Fraction 3 and the female fraction 4, which represent the major proteins in the blood, appear to serve as carriers of lipids to the ovaries, besides most likely providing proteinaceous yolk precursors to the same. Fractionations made with ovarian homogenates seem to indicate that the lipids and sugars bound to such proteins may become freed at entry into the ovary.2. Cardiac-allatectomy has been found to result in a pronounced accumulation of proteins in the blood, and also in changes in their chemical composition. In such animals there is a tendency with aging for the loss of lip...