158 GENERAL BIOLOGY OF MICRO-ORGANISMS 



ally the cytoplasm also. The nucleus of each of these masses 

 (sporoblasts) then divides many times. Each nucleus, together 

 with a small amount of protoplasm, separates and then elongates 

 into a slender thread-like sporozoit (14X1/0 As many as io,ooc 

 of these may be produced in one oocyst. The cyst bursts into the 

 body cavity of the mosquito and the motile sporozoits circulate 

 through the body of the insect and eventually assemble in the cells 

 of the salivary glands. From these they escape with the secretion 

 and gain entrance to the wound made by the mosquito in biting. 

 Babesia. A number of parasites of the red blood cells are 

 classed in the genus Babesia (Piro plasma). These resemble the 

 members of the preceding genus very closely but multiple division 

 (segmentation) does not seem to occur in the asexual cycle. The 



v G^~ H 



FIG. 8c. Babesia muris. A, Young form in a red blood cell. B, Form with 

 two nuclei. C and D, Binary division. E and F, Multiple infection; ameboid 

 forms in F. G, An exceptionally large individual (gametocyte?). H, Form with a 

 thread-like process (flagellated stage?). (From Doflein after Fantham.) 



multiplication seems to be by longitudinal division into two 

 daughter cells. The characteristic form is pear-shaped, but 

 irregular amoeboid 'forms are also common. Flagellate stages 

 existing in the blood plasma have also been described. The sexual 

 cycle takes place in a tick, and is in part analogous to that described 

 for Plasmodium. The stages are not fully known, but the infec- 

 tivity of the tick is transmitted to the offspring in the case of the 

 Texas-fever tick (Rhipicephalus (Boophilus) annulatus). 



Nosema. The sporozoa above described all belong to the 

 Telosporidia, organisms which end their individual existence at 

 the stage of spore formation. A second large subdivision of the 

 sporozoa is named Neosporidia. In this group the spores are 

 formed without terminating the existence of the individual. The 



