SPOROZOA 



411 



granules in its cytoplasm, and when full-grown the chromatin 

 of the nucleus is reduced by expulsion of the karyosome. The~ 

 matured cell, macrogamete, is then ready for union with the 

 microgamete. The growing cell destined to give rise to the male 

 sexual elements attains a large size and possesses a pale cytoplasm. 

 It is called the microgametocyte. Its nucleus divides many 

 times, the small nuclei accumulate near the surface of the cell 

 and each escapes with a small portion of protoplasm as a slender 

 motile microgamete. The penetration of one of Jthese into the 

 macrogamete produces the fertilized oocyst, which forms a thick 



FIG. 181. Eimeria steida. a, Young agamete (merozoit). b, Epithelial cell 

 invaded by three young agametes. c, d and e, Stages in the multiple division of the 

 agamete. /, Young macrogametocyte. g, Full-grown macrogametocyte. (From 

 Doflein after Hartmann.) 



wall about itself and escapes to the external world. Here, the 

 fertilized cell divides to form eight cells, sporozoits, which are 

 enclosed within four oval spores (two in each) within the wall of 

 the oocyst. If this cyst is ingested by another rabbit the cycle 

 of development starts anew. 



Coccidiosis is a very common disease in rabbits. The animal 

 suffers from severe diarrhea and loss of appetite, and becomes 

 emaciated. Young rabbits often die of the disease. Diagnosis 

 is readily made by finding the oocysts in the feces. Children 

 have been found to be infected with this organism. Cattle, 



