216 



PROTOZOA. 



macrogametes which are fertilized by the microgametes, and then 

 encyst, pass to the outside, and serve for the infection of other 

 animals. The contents of the cyst begin to divide, sooner or 

 later, into sporoblasts (in Coccidium, four) containing spores, the 



FIG. 156. Coccidium cuniculi, from the liver of the rabbit (from Wasielewski. a, & r 

 young Coccidia in the epithelial cells of bile duct, the nucleus of the cell in the 

 upper process; c, encysted; d, e, contraction of protoplasm; t, h, g, spore forma- 

 tion; /, ripe spore with two germs and a residual body. 



process being completed only after entrance into a new host. 

 Each spore forms one or more sporozoites, a portion of the sub- 

 stance being left behind. Coccidium cuniculi (oviforme) in the 

 liver of mammals, especially rabbits (rare in man), producing 

 cheesy granules. C. perforans in the intestine of rabbits, rare in 

 man. 



Order III. Haemosporida. 



In structure and development these are much like the Coccidiae ; 

 they live in blood corpuscles. The forms occurring in man pro- 

 duce malaria. Here, also, there are endogenous (autoinfecting) 

 and exogenous generations transferring the parasites to other 

 hosts. The parasites in the corpuscles (fig. 157, a to d) grow and 



abed e f g 



FIG. 157. Plasmodium laverni, var. quartana (from Wasielewski, after Labb6), from 

 the blood of a malarial man. a, newly infected blood corpuscle; b, somewhat 

 larger germs; c, full-grown parasite with strong pigmentation; d, rounded form 

 with large nucleus; e, beginning of germ formation; /, rosette of germs around a 

 residual body; g, germs set free by degeneration of corpuscle. 



divide, producing ( daisy-like forms' characterized by little accu- 

 .mulations of pigment derived from the haemoglobin of the blood. 



