An attempt to compare the nature of yeast phase cultures of the two strains and hemagglutination test was made and the findings gained were as follows: 1. In the Japanese strain, the large form fungi werc predominant even on young cultures, and on the contrary, the culture of the American strain was composed of the small form organisms irrespective of the stage of growth.
2. The count of fungi on 3-day cultures attained to (5-6)×10(6)/mg, (9-10)×10(6)/mg in the Japanese and American strains respectively, and decreased gradually with the passage of time.
3. The ratio of viable cells on 3-day culturos was 76 per cent in the former strain and 65 per cent in the latter, and it decreased significantly with the passage of time, especially in the former strain. 4. The lethality of CF-1 mice interavenously inoculated with 1.0 mg of 3-day cultures was found to be 100 per cent in both strains, and when 7-day cultures are applied, no alteration was revealed in the American strain but it was as low as 20 per cent in the Japanese strain. No lethal case was induced by fortnight cultures of either one of the two strains. 5. The pathologic features produced were represented by productive and granulomatous inflammations in the reticulo-endothelial system, and distribution of the small form organism in the reticulo-endothelial cells was more distinguishable in the American strain than in the Japannse one. 6. The characteristic appearance of the experimental infection in mice was disemination of the small form organisms in the reticulo-endothelial system in both strains, but the large form ones were also seen in necrotic lesions of survived mice, and this incidence was more frequent in the Japanese strain. 7. The data obtained from hemagglutination tests suggested that the protein fraction might be common in both strains, and the polysaccharide fraction had somewhat strain-specificity. The above varieties proved were not always sufficient to differentiate the one from the other as it had been observed in isolated strains in the North America.