530 



BIOIJICY OF THE I'h'OToZOA 



gametes fuse, a maeroganiete being fertilized by a single micro- 

 gamete (g). The fertilized cell resulting from this fusion is the 

 zygote in which the pronuclei fuse. The fertilization nucleus then 

 divides and the two products divide again before the protoplasm 

 divides into four parts, one about each of the nuclei. This process, 

 or metagamogony, results in the formation of four sporoblasts within 

 the sporocyst and each sporoblast has its own individual protective 



Fig. 212. — Eimeria Schubergi. Sporozoites penetrate epithelial cells and grow 

 into adult intracellular parasites (a). When mature, the nucleus divides repeatedly 

 (b), and each of its subdivisions becomes the nucleus of an agamete (c). These enter 

 new epithelial cells and the cycle is repeated many times. After five or six days of 

 incubation, the agametes develop into gamonts; some are large and stored with yolk 

 material (d, e, ./'), others have nuclei which fragment into chromidia which become 

 the nuclei of mierogametes (d, h. i, j\. A maerogamete is fertilized by one micro- 

 gamete (g) and the zygote forms an oocyst (k). This forms four sporoblasts, each 

 with two sporozoites (/). (After Schaudinn.) 



capsule (/). The nucleus of each sporoblast then divides and two 

 independent cells are formed in each sporoblast. These indepen- 

 dent cells arc the sporozoites. To recapitulate: Sporozoites come 

 from sporoblasts; sporoblasts from zygotes; zygotes from fusion of 

 gametes; gametes from gametoevtes, these from gamonts; gamonts 

 from agametes; agametes from agamonts, and agamonts, originally, 

 from sporozoites. 



