242 ILLINOIS BIOLOGICAL MONOGRAPHS [452 



EXPLANATION OF PLATE 



Figures 240-255. Leidyana erratica (Crawley) Watson. 



Fig. 240. The protomerites are visible as slightly dense areas; the transparent 

 layer has become still wider. X 60. 



Fig. 241. The outside layer is much wider than before and the inner mass smaller 

 because of the exudation of liquids. The line of separation be- 

 tween the two sporonts is now obliterated and the cyst is a homo- 

 geneous mass. X 60. 



Fig. 242. The protoplasm is collected in small spherical masses. X 60. 



Fig. 243. Section of a sporont stained on the slide, showing the longitudinal 

 striations and the myonemes, which form a horizontal network of 

 fibrillae. X 500. 



Fig. 244. A segment of the cyst in the stage shown in Fig. 242. The gametes 

 are being formed from the outer parts of these protoplasmic 

 masses. X 245. 



Fig. 245. Six spore dutcs are indicated by orange colored condensation discs on 

 the surface of the cyst mass. X 60. 



Fig. 246. The spore ducts have grown from the periphery inward to the central 

 part of the mass. X 245. 



Figs. 247, 248. The ducts extending outward from the periphery into the trans- 

 parent cyst wall. X 245. 



Fig. 249. A mature cyst from which the spores are being extruded in chains, 

 X 245. 



Fig. 250. Cross section of an intestine heavily infected with parasites; the gre- 

 garines remain in the epithelial region of the intestine rather than 

 among the food masses where they would easily be swept along by 

 peristaltic movement. 



Fig. 251. A gamete taken from a cyst which was crushed at the end of about 

 thirty hours. Diagramatic. 



Fig. 252. Two isogametes which have just fused, from a cyst of about thirty-five 

 hours. Diagramatic. 



Fig. 253. A later stage in the fusion of the isogametes. Diagramatic. 



Fig. 254. A zygote formed by the fusion of the two gametes. X 810. 



Fig. 255. Ripe spores from a fully developed cyst of about forty-eight hours, 

 X 810. 



