The hare strain HT of Toxoplasma gondii which was reported in the previous paper was tested immunologically and also pathogenicity for the laboratory animals and was examined in comparison with known toxoplasma strain RH. The data obtained are summarized as follows. 1. The strain HT indicated high virulence for mice and death occurred generally in 5∿6 days after intraperitoneal inoculation, almost the same as the RH; however the number of parasites in mouse peritoneal fluid was very small in comparison with the strain RH. 2. For rabbit and guinea pig, the strain showed very low virulence. In rabbit, even resulting from intracerebral inoculation, only fever reaction occurred and the general conditions ran always normal afterward. 3. Immunologically, by the use of cross complement-fixation test, this strain was identified as Toxoplasma gondii. 4. At first, the isolated strain HT had revealed no reactivity in vitro in case of dye test with the rabbit sera infected with the strains HT and RH, however the isolated strain had showed the ability to produce cytoplasm-modifying antibody reacting with the antigen RH. After about more than 50 mouse passages, the strain revealed reactivity in vitro the same as the strain RH. The above facts must be remembered for serological identification of the newly isolated strains by the dye test
