94 SOME MINUTE ANIMAL PARASITES 



gestive of spirochaetes, are formed (Fig. 21, D, <3), 

 each with relatively much nuclear material and a 

 cytoplasmic body. Writhing about, they move 

 rapidly here and there, often dragging the remains 

 of the parent cell with them. 



The females (Fig. 21, C, ? ), meanwhile, have 

 burst the blood-corpuscle imprisoning them, have 

 given off a small part of their chromatin (Fig. 21, 

 Z), ? ), and are ready for fertilization. Union with 

 the male, or microgamete (Fig. 21, E), is followed 

 by an extraordinary activity on the part of the 

 female, which, once fertilized, proceeds to move 

 actively over the surface of the stomach of the 

 mosquito, and is known as the vermicule, from its 

 wormlike gliding movements, or as the ookinete 

 (Fig. 21, F), Gradually it bores its way through 

 the mosquito's stomach and reaches the subepithelial 

 layers, where it becomes rounded (Fig. 22, A) and 

 non-motile, but continues to grow, so producing 

 marked bulgings on the outside wall of the stomach 

 into the body cavity. Nor is its increase in size its 

 sole manifestation of activity. Its nucleus begins 

 to divide (Fig. 22, B), and the division is repeated 

 a very great number of times (Fig. 22, C). The 

 body cytoplasm gradually collects around each 

 nucleus, and the segments of the zygote, now 

 known as sporoblasts, soon begin to be studded with 

 numerous protrusions (Fig. 22, D). These take the 

 form of slender sickle-like bodies, which, when fully 

 formed, separate from the residual mass within 

 (Fig. 22, E). Each tiny body so formed is called a 

 sporozoite (Fig. 22, E), and the cyst produced by the 



