36 ILLINOIS BIOLOGICAL MONOGRAPHS [246 



slip and slide until they form a perfect sphere ; central spherical area left 

 between the two sporonts; gelatinous layer forming around the rotating 

 sphere ;the outer layer wider and distinct. ' ' The time for the first com- 

 plete rotation of the solitary individual was one and one-eighth minutes. 

 Approximately this rate is retained during sixteen rotations. The rota- 

 tions then becomes slower as the mass more and more nearly approxi- 

 mates a sphere. Two and one-half minutes, four minutes, and five min- 

 utes are recorded for successive rotations. At the end of forty-five min- 

 utes the cyst was complete but still slowly rotated at the rate of one ro- 

 tation in from four to five minutes. When next observed, two hours la- 

 ter, motion had ceased and there was present a gelatinous layer in thick- 

 ness one-third the radius of the cyst. 



Fully formed cysts which are still in the process of rotation were 

 frequently taken from the host and they continue to rotate a half hour or 

 more after removal. 



Cyst Development and Dehiscence 



When the mass has finished rotating, it is a beautifully homogen- 

 eous, opaque, gray spherule surrounded by a thick, transparent, cyst 

 wall fifty micra in thickness or half the radius of the inner mass. The 

 mass begins to disintegrate in twelve to fifteen hours, the protoplasm 

 becoming arranged in many dense areas (Fig. 242). The diameter of 

 the inner mass decreases and that of the transparent cyst wall increases 

 by the exudation of water from the inner regions. In twenty-four hours 

 the protoplasm within the cyst wall has begun to shrink from the peri- 

 phery. Five hours later (29 hrs.) the spore ducts are clearly indicated 

 (Fig. 245) by dense accumulations of protoplasm on the periphery or 

 orange colored discs on the cyst surface. From three or four to a dozen 

 of these discs are delineated. The orange color is due to an accumulation 

 of orange colored oil which dissolves and loses its color in ether. Soudan 

 III stains it red. The oil can be pressed out from the cyst in large 

 globules. The origin of this oil in the cyst is, of course, the endoplasm of 

 the sporonts. The protomerite is tan in color and probably contains con- 

 siderable oil ; the deutomerite may contain as much or more but the color 

 is obscured by the great number of protoplasmic granules which render 

 the whole very opaque. 



After thirty-five hours, the ducts leading from the periphery to the 

 center of the cyst mass appear ; they resemble the spokes of a wheel. In 

 a few more hours the spore ducts begin to project from the surface of the 

 sphere; the center is depressed (Figs. 247, 248). By this time the indi- 

 vidual spores are visible within the mass ( Fig. 246 ) . At the end of from 

 forty-two to sixty hours, the spores are liberated (Fig. 249). Although 

 from one to a dozen spore ducts begin to grow outward, not more than 



