PARASITISM AMONG PROTOZOA 



107 



Fig. 61— A TYPICAL LTFE CYCLE OF A SPOROZOAN— 

 EIMERIA SCHUBERGI 



A germ, called a sporozoite, enters an epithelial cell, a, and grows to a large intracellular 

 organism; its nucleus divides, b, and the cell breaks up into many spores, c. These enter new 

 cells and repeat the cycle. Ultimately two different kinds of individuals are formed by the 

 spores. One kind (d,c,f) is large and has a heavy, granular protoplasm; this is a female type 

 or macrogamete, g. The other type grows into a transparent cell which forms a multitude of 

 very fine sperm-like cells, the microgametes (h,i,j,s). The egg is fertilized by a microgamete. 

 This is followed by an entirely different kind of sporulation. The fertilized nucleus divides 

 twice and four cells are formed, each having a capsule about it (£,/). Within each of these, 

 two germs, or sporozoites, are formed, and these in a new host, repeat the cycle 



After Schaudinn 

 Magnification, 480 



repeated for a period of five or six days, with the result that 

 great numbers of intestinal cells are destroyed. Ultimately, the 

 agametes grow into gametocytes, which are of two kinds — one 

 is well stored with food substance and becomes the macroga- 

 mete, or egg-like sexual element (Fig. 61 / and g) ; the other, 

 after repeated nuclear divisions, forms a great number of deli- 

 cate, minute, motile microgametes, or spermatozoa-like cells 

 (Fig. 61 h, i, and ;'). A macrogamete is then fertilized by a 

 microgamete and the resultant zygote immediately secretes a 



