504 



PROTOZOOLOGY 



injected blood into gut lumen, isogametes, 5.5-6/i long, are produced; 

 isogamy results in motile club-shaped ookinetes, 7-12m long, which 

 pass through gut wall and invade larger ova (1-2, in one case about 

 50, ookinetes per egg) ; each ookinete rounds itself up into a sporont 

 7.5-12/x in diameter, which grows in size and whose nucleus divides 

 repeatedly; thus are produced multinucleated (4-32 nuclei) amoe- 

 boid sporokinetes, up to 15m long, which now migrate throughout 

 embryonic tissue cells of tick, many of which cells develop into 



Fig. 236. a-d, Babesia bigemina, X3000 (Nuttall); e-h, B. bovis, 

 X3000 (Nuttall); i-1, Theileria parva, XBOOO (Nuttall); m-s, Dactylo- 

 soma ranarum (m-q, schizogony; r, s, gametocytes), X2700 (Noller). 



salivary gland cells; sporokinetes develop into sporozoites before or 

 after hatching of host tick; sporozoites bring about an infection to 

 cattle when they are inoculated by tick at the time of feeding. Texas 

 fever once caused a considerable amount of damage to the cattle 

 industry in the southern United States to which region the distribu- 

 tion of the tick is limited. 



B. bovis Starcovici (Fig. 236, e-h). In European cattle; amoeboid 

 form usually rounded, though sometimes stretched; 1-1. 5^ in dia- 

 meter; paired pyriform bodies make a larger angle, 1.5-2/x long; 

 transmitted by Ixodes ricinus. 



