(5) The globular body divides into a number of “sporoblasts,” which become scattered through the tissues of the larval or nymphal tick, as the case may be. (6) The sporoblasts themselves divide into a large number of sporozoites, which are small uninucleate bodies, somewhat resembling blood piroplasms. The sporozoites collect in the salivary glands of the tick. They are inoculated into the vertebrate when the tick next feeds. The chief species of _Babesia_ and their pathogenic importance may be listed thus:-- (1) _Babesia bovis_ (Babes) produces infectious hæmoglobinuria of cattle in Europe and North Africa. It is transmitted by _Ixodes ricinus_. A similar parasite also occurs in deer. (2) _Babesia bigemina_ (Smith and Kilborne) produces Texas fever, tristeza, or red-water in cattle in North and South America, South Africa and Australia. It is transmitted by _Boöphilus annulatus_ in North America, by _B. australis_ in Australia, South America, and the Philippines, and by _B. decoloratus_ in South Africa. The parasite is from 2 µ to 4 µ long, and from 1·5 µ to 2 µ broad. _Babesia bigemina_ may be the same parasite as _B. bovis_. (3) _Babesia divergens_ (MacFadyean and Stockman) is a small parasite. It is found in cattle suffering from red-water in Norway, Germany, Russia, Hungary, Ireland, Finland, and France, and is transmitted by _Ixodes ricinus_. (4) _Babesia canis_ (Piana and Galli-Valerio) gives rise to malignant jaundice or infectious icterus in dogs in Southern Europe, India, and other parts of Asia and North Africa, where it is transmitted by _Rhipicephalus sanguineus_. In Africa generally, especially South Africa, the disease is transmitted by _Hæmaphysalis leachi_. _Babesia canis_ varies from 0·7 µ to 5 µ, the size depending partly on the number of parasites within the corpuscle. It averages about 3 µ. It has been cultivated in Bass’ medium (glucose and infected blood), see p. 172. In India _Piroplasma gibsoni_ (Patton) infects hunt dogs and jackals. It is annular or oval in shape. (5) _Babesia ovis_ (Babes) produces “Carceag,” a disease of sheep in Roumania, the Balkan Peninsula, Italy, and Transcaucasia. It varies in size from 1 µ to 3 µ. It is transmitted by _Rhipicephalus bursa_. The parasite has recently been recorded from Rhodesia. (6) _Babesia caballi_ (Nuttall and Strickland) causes “biliary fever” in equines. The parasite occurs in Russia, Roumania, and Transcaucasia. It varies in size from 1 µ to 2 µ. It is transmitted by _Dermacentor reticulatus_. It should be mentioned that _Nuttallia equi_ also causes “piroplasmosis” in equines, with symptoms of hæmoglobinuria and jaundice in Italy, Sardinia, many parts of Africa, Transcaucasia, India, and Brazil. In Africa it is transmitted by _Rhipicephalus evertsi_. It has been shown experimentally that a horse recovered from _Babesia caballi_ was susceptible to the inoculation of _Nuttallia equi_ blood.