144 



THE ANIMAL PARASITES OF MAN 



becomes loaded with chromatoid and plastinoid granules (fig. 69, J, $ ), while 

 the microgametocyte has its nucleus divide to form a number of bent, rod-like 

 portions (fig. 69, J, <?). The macrogametocyte gives rise to a single macrogamete, 

 which forms a cyst wall for itself, leaving a thin spot (micropyle) for the entry 

 of the male (fig 69, K, ? ). The microgametocyte gives rise to numerous small, 

 biflagellate microgametes (fig. 69, K, ) around a large, central residual mass, 

 from which they ultimately break free, and swim away. When a macrogamete 

 is reached, the microgamete enters through the micropyle (fig. 69, L) which 

 then closes, thus excluding the other males and applies itself to the female 



FIG. 69. Eimeria avium. Diagram of life-cycle. For explanation see text. 

 (After Fantham.) 



nucleus (fig. 69, M). Nuclear fusion occurs, the oocyst (encysted zygote) being thus 

 produced. Sporogony then ensues. The oocyst (fig. 69, H) at first has its contents 

 completely filling it. They then concentrate into a central spherical mass (fig. 69, o) 

 which gradually becomes tetranucleate (fig. 69, p). Cytoplasm collects around each 

 nucleus, and four sporoblasts are thus formed (fig. 69, Q). Each sporoblast becomes 

 oval (fig. 69, R) and produces a sporocyst. Ultimately two sporozoites are formed in 

 each sporocyst or spore, at first lying tete-beche (fig. 69, s), but finally twisting 

 to assume the position most convenient for emergence (fig. 69, T) when they reach a 

 new host. The period of the life-cycle of Eimeria avium (as well as the details 



