Organ specifities in each embryo were investigated in the sensitized rabbits with each embryonic organs such as brain, kidney, mucous membrane of small intestine and etc. And the following results were obtained. 1. Vicissitudes of antibody titers in the sensitized rabbits with various organs of dogs showed a sudden increase, in all, after the first and the second week and maximum in the fifth and sixth week. Some of them had relatively high titers. No significant difference in the course of sensitization with each embryonic organs. 2. The Congo Red Indeces of the sensitized rabbits with each embryonic organ antigens of dogs had increased according to the repeats of the sensitizations. 3. The erythrocytes sedimentation rates of the sensitized rabbits with each embryonic organ antigens of dogs were almost stable inspite of repeated sensitizations using various kinds of organ antigens. 4. No significant changes were noted of erythrocytes and of hemoglobin of the sensitized rabbits with each embryonic organ antigens of dogs inspite of repeated sensitizations using various kinds of orgaan antigens. However, there were some tendencies of anemia in a few rabbits after repeated sensitizations. 5. Leucocytes count and its differentials of the sensitized rabbits with each embryonic organ antigens ef dogs; with repeated sensitizations many showed leukocytosis, and in differential two groups were noted, the one of which revealed pseudoeosinophilia with lymphopenia and the other lymphocytosis with pseudoeosinopenia. 6. All the cases of the sensitized rabbits with each embryonic organ antigens of dogs had some weight losses on sensitizations, especially marked initially. 7. On the same days of the administrations of these antigens, all the cases of the sensitized rabbits with each embryonic organ antigens of dogs had rising body temperatures of about 1.0°C. 8. In the cross reactions between the sera of the sensitized rabbits with each embryonic organs of the dogs and the various organ antigsens of the dogs, the antibody titers for these organ antigens were the highest in all the sensitized rabbits. In the cases with other organ antigens, the antibody titers were lower, and kept up rather short time in the blood. Simultaneously the relative organ specifites could be recognized especially for brains which stemed from ectoderm comparing with other embryonic organs.