(1) A new species of protozoan parasite in the Cape dassie is described for
which the name Babesia thomasi is proposed.
(2) This parasite is only slightly pathogenic for normal animals but fatal for
splenectomised Cape dassies.
(3) A premunity develops in recovered animals.
(4) Attempts at transmission to cattle and guinea-pigs failed.
(5) The natural transmission is unknown.
(6) The Cape dassie is not susceptible to Theileria parva infection.