517 



where all of the stages are drawn with the aid of a camera lucida to 

 the same scale. The small rounded sporozoite grows until about the 

 size of a spore, and at this stage appears very much like a spore al- 

 though it does not have the same densely homogeneous structure. It 



Fig. 3. Young sporozoites entering muscle bundles about the intestine. Camera 

 lucida X 2000. 



soon becomes amoeboid and, when slightly larger than a spore, is va- 

 riable in shape (fig. 2). At this stage or slightly later, the amoeboid 

 organisms begin to penetrate the muscle bundles surrounding the 

 intestine and other organs. By amoeboid movements they work their 



Fig. 4. Adult amoeboid individuals in the muscle bundles. Camera lucida X 2000. 



way between the muscle cells where they lie until mature growth is 

 reached and they are ready for spore-formation (fig. 3). 



The adult organism has few characteristic marks of structure. 



