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X-irradiation and received orthotopic grafts ofovarian tissue from donors of the same strain. A linear relationship was demonstrated between log. age and the number of oocytes in both normal ovaries and orthotopically grafted ovarian tissue of G strain (CBA/Fa-a*) mice. It was calculated from the regressions that an average of 65% of the oocytes in the implanted tissue was lost within a few days of grafting. However, the subsequent rate of oocyte loss was reduced so that the potential reproductive life of the recipient mice was not drastically shortened. The average size of litters born to graft recipients was less than that recorded in normal mice with the same number of oocytes. It was considered that obstruction or splitting of the ovarian capsules of the grafted animals resulted in the loss of many ova. Shortage of oocytes or mature follicles did not appear to be a major factor in determining litter size. Other variables, including the interval between sterilization of recipients by X-irradiation and grafting, the age of donors and the volume of graft material, were also investigated in relation to the fertility of the grafted mice. Increased foetal résorption in two strains was noted.

SIJMMARYInterferon was produced in chick embryo cell cultures orjn chick embryos by five viruses and in mouse embryo cell cultures or mouse lungs by two viruses. The slopes of the log dose response lines for the five chick interferons were compared by using vaccinia virus as the assay virus. Analysis of variance showed that they did not differ significantly. Partially purified interferon gave the same slope as the crude preparations. These findings allowed a comparison to be made of relative yields of interferon induced by different viruses in the same cell system. Viruses differed widely in their ability to induce interferon. Chikungunya virus induced about 70 times more interferon than did vaccinia or Newcastle disease virus and 2.6 times more interferon than Kumba virus. The slopes of the log dose response lines for two interferon preparations were compared by using Chikungunya virus as the assay virus. Analysis of variance showed that they were not significantly different. A comparison of the vaccinia and Chikungunya assays for interferon showed that the Chikungunya assay was approximately 2-9 times more sensitive when the amount of interferon depressing the plaque count by 50 yo (PDD 50 doses) were compared. An analysis of variance showed that the difference in slope between the two assays was small but approaching significance. Mouse interferon, induced by two viruses, yielded parallel dose response lines. However, the slope of the curves for mouse interferon was significantly different from that for chick interferon. Because of this difference in slope, interferon production by the same virus in the two cell types could not be validly compared.