283] STUDIES ON GREG ARINES WATSON 73 



toplasm which gives to them a blackish appearance. The deutomerite 

 stains a fairly homogeneous shade, and the small granules here do not 

 absorb as much of the stain as do the larger protoplasmic granules. 



The epicyte is colorless and very thin, even at the septum. Longitu- 

 dinal striations are discernible. This epicyte is much more resistant 

 than in many gregarines studied, for animals remain alive on the slide 

 in a water medium or in normal saline for many hours, and when they 

 finally become immotile, retain their shape. After several days on the 

 slide, they have been noted to be intact with the body only a little more 

 nearly globular from osmosis than in the normal parasites. This may 

 be due to the thinness of the epicyte and its great permeability. Myone- 

 mes were seen in stained sectioned specimens as deeper staining dots, 

 larger than the deutomerite granules and lying along the periphery of 

 the endocyte in the longitudinal striations. 



The nucleus of sporonts is an elongate ellipsoid, generally placed 

 diagonally and reaching almost entirely across that part of the deutome- 

 rite in which it lies. In large specimens, it approximates 55 x 30/z. It 

 contains one large spherical or slightly ovoidal karyosome which stains 

 evenly and lightly throughout with Ehrlich's hematoxylin. The nu- 

 cleus is not visible in vivo in the large and dense individuals. In young 

 specimens, it is spherical, becoming ellipsoidal us the sporont stage ap- 

 proaches. 



The trophozoite is much less dense than the sporont. The epimerite 

 is a round, sessile, transparent knob. 



The sporozoite is a deeply staining, spindle shaped body which pene- 

 trates the cell at is free end, becomes embedded, grows, and absorbs the 

 host cell which it entered. The whole trophozoite, not merely the epime- 

 rite, lies embedded and after it has destroyed the originally entered cell 

 distorts and compresses those adjoining. It remains embedded until it 

 has practically outgrown the cells of the epithelium and easily escapes 

 into the lumen through the canal it has formed by cell destruction. The 

 trophozoite is able to move about while embedded. In cross sections of 

 the intestine the parasite, still embedded, is sometimes cut crosswise, in- 

 dicating that it lies with its longitudinal axis parallel to that of the host, 

 and in one instance it lay with the protomerite pointed toward the lumen 

 rather than toward the mesothelial wall, the normal position. 



The gliding movement common to most Polycystids is functional 

 here and the animal moves forward very rapidly in a straight line, often 

 with a constant turning of the protomerite from side to side which af- 

 fects neither the rapidity nor the direction of motion. Progression has 

 been observed at the rates of 6.5/t and 7.5/i per second. Each of these 

 rates is for a different specimen and each movement extends at a uniform 

 rate over several minutes. No gelatinous stalk was seen trailing the ani- 



