276 THE PATHOGENIC HEMOSPORIDIA 



The larva changes into the adult form on the ox and transmits the 

 disease with its first feeding. 



Lounsbm-y ('04), after three years of experimentation and obser- 

 vation in South Africa, proved that Babesia canis of the dog is con- 

 veyed by the tick Hemophysalis leachi, and not, as in Texas fever, by 

 the larva from infected ticks, but only by adult ticks reared from the 

 eggs of infected ticks. Later, Christophers ('05-'07) demonstrated 

 that another tick, Rhipicephalus sanguineus, Latr., is also capable of 

 transmitting the disease, and he believes this to be the primary agent 

 in transmitting European dog piroplasmosis. According to Chris- 

 tophers, the larvae or the nymphs, as well as eggs, may become infected 

 directly from the dog, and so may carry the disease into the later 

 developmental stages of the insect. The latter means of transmission 

 seems to be the only one in the case of East Coast fever, where, accord- 

 ing to Lounsbury ('04) and Theiler ('05), the parasite (Babesia parvum) 

 can be conveyed only by the larva which becomes infected, the infec- 

 tion being carried to and transmitted by the nymph, while infected 

 nymphs convey the infection to adults. The variations in regard to 

 the mechanism of transmission, especially the time factor, indicate that 

 obligatory changes in the life history take place in the insect's body. 

 What these changes are must be very difficult to ascertain, because of 

 the minute size of the parasite. The first observations to this end were 

 made by Koch ('05) upon the organism of East Coast fever in the 

 digestive tracts of different ticks (Rhipicephalus auMralis, R. evertsi, 

 and Hemaphysalis egyptium). Here they become stellate in form 

 and often appear in couples, a circumstance leading Koch to surmise 

 some type of conjugation. Globular and peculiar club-shaped forms 

 were also observed, but their significance was not made out (Fig. 

 108, E). 



Evidence is accumulating to show that, as in the case of Plas- 

 modium malarice, a sexual cycle takes place in the tick, and it is not 

 oversanguine to state that the various conflicting observations on 

 "flagella" and other structures formed by the parasite at different 

 stages will shortly be straightened out in a consistent life history. 



First, as to the so-called "flagella." Leaving out of account Miya- 

 jima's unconfirmed observations on a crithidia-like stage of Babesia 

 parvum, there are repeated references to flagella formation, especially 

 in the case of the dog parasite Babesia canis. Here the descriptions 

 by Bowhill and Le Doux ('04), Nuttall and Graham-Smith ('06), 

 Kinoshita ('07), and Breinl and Hindle ('08) are in agreement with 

 the observations of Lignieres ('03) on Babesia parvum, and with 

 Fantham ('05) on Babesia muris. According to Kinoshita, the flagellum 

 which he, with Doflein and many others, interprets as a microgamete 

 invariably takes its origin from the blepharoplast (Fig. 107, C, E). It 

 is not smooth and uniform, like a flagellum, but possesses granular 



