30 ILLINOIS BIOLOGICAL MONOGRAPHS [240 



tomerite first, through the mesothelial walls of the intestine into the coe- 

 lom, and in sections of the host some specimens have actually been found 

 in the coelom lying close to the coelomic epithelium of the intestine. Dur- 

 ing the boring process the muscular tissue in the wake of the parasite is 

 destroyed, leaving the surrounding tissue shredded and contorted. 



The adult parasites seem to prefer lying loose between lobes or clus- 

 ters of intestinal cells rather than living in the open lumen. The inter- 

 stices of the lobes are very frequently occupied by large adult gregarines. 



The sporozoite is spindle shaped and swells in the lumen. It pene- 

 trates the free end of a cell between the cilia and undergoes develop- 

 ment within the cell. The first trophozoic stage I have seen is the small, 

 completely formed body without a protomerite, lying embedded with its 

 epimerite at the distal end of the cell next to the mesothelial layer. It 

 undergoes considerable growth here with the consequence that the cell 

 ♦ is destroyed and the parasite comes to lie in a self-formed cyst between 

 two cells, often affecting parts of these cells and causing the cells for 

 some distance around to b6 greatly compressed. Then the epimerite dis- 

 appears and the protomerite develops and becomes more or less flattened 

 against the basement layer of the cell. The trophozoites emerge into the 

 lumen through the space left by the originally destroyed cell. The nu- 

 cleus of the trophozoite of Stenophora lactaria is spherical; it begins 

 however to acquire its ellipsoidal form while still in the intercellular 

 stage. 



The Gregarinidae 



The parasites of this family become associative *while they are quite 

 immature and long before they are ready to form cysts. The shape of 

 the sporonts remains fairly constant whether they are young or fully ma- 

 ture. The sporonts of the genus Oregarina are always more or less obese, 

 and very frequently dolioform. The protomerite is much larger than in 

 the Stenophoridae in comparison to the size of the body. In length, it 

 varies from one-half to one-eighth the total length of the body. It is fre- 

 quently hemispherical and as often cylindrical, rounded in front, but it 

 is more than twice as high as wide ; it is rarely conoidal. There is some- 

 times a slight indentation at the apex. 



The epicyte is fairly thick tliroughout but is thicker at the anterior 

 end of the body and at the septum than elsewhere. 



The deutomerite is nearly always wider than the protomerite. It is 

 fairly regular in shape throughout the family, being generally widest at 

 the middle or slightly anterior thereto and gradually tapering both an- 

 teriorly and posteriorly. The posterior end is always rounded ; it is 

 never sharply acute. 



