154 ILLINOIS BIOLOGICAL MONOGRAPHS [392 



is differentiated into two regions. The outer layer (ectoplasm) surrounds 

 the body as a thin, light-staining region, while the endoplasm being den- 

 ser and of more or less granular structure filled with spores especially in 

 the central portion. 



Spore: Johnston and Bancroft describe as follows: 



Form somewhat variable, caused by the reduction in length. Oval, 

 egg-shaped or nearly circular in front view. Sutural ridge slightly thick- 

 ened. Two pyriform polar capsules are located at the anterior end. 

 Sporoplasm with an iodinophilous vacuole (2/x in diameter), shows usually 

 two distinct nuclei, rarely but one. Dimensions: length variable, diameter 

 of circular form 7 to 8/x, breadth 8 to 10/x, thickness about 6;u, thickness of 

 shell 1/x, polar capsules 4 to Sfji, by 2fx, length of polar filament 90 to 98ju 

 (acids or alkalies). 



MYXOBOLUS AUREATUS Ward 

 [Figs. 643 to 649] 

 1919 Myxobolus aureatus Ward 1919 : 49 



Habitat: Between the ectodermal layers of the fin membrane of 

 Notropis anogenus; Put-in-Bay, Lake Erie (August). Out of thirty fish, 

 two to three cm. in length, seven were found to be infected. The infected 

 fish were not inferior in size or vigor to others of the same species. The 

 most heavily infected one was the most vigorous of all. The number of 

 cysts in the individual fish, varied from one to forty, being confined in the 

 fin. The cysts are always separated from each other, tho in a few instances 

 they were apparently connected. 



Vegetative form: The parasite forms cysts between the ectodermal 

 layers of the fin membrane. The cyst is a smooth margined ellipsoid, 

 measuring from 1 to 1.6 mm. in layer diameter and from 0.8 to 1.2 mm. 

 along its transverse axis. The opaque cyst is of a clear orange yellowish 

 color. This gilt color is contained in the cyst wall, fading away in alcohol 

 and formol. The chromatophores of the skin of the host are distinctly 

 more abundant on the cyst than in other parts of the skin, and the older 

 the cyst the more abundant the chromatophores. The wall of the cyst is 

 noticeably tough and thick. In section, the protoplasm shows a poor 

 differentiation into ectoplasm and endoplasm. The former granular and 

 reticular, covers the entire surface as a thin layer, while the latter is highly 

 vacuolated, containing only mature spores. Polysporous. 



Spore: Ovoid; slightly pointed anterior and rounded posterior ends in 

 front view; slightly compressed in lateral view. Sutural ridge distinct. 

 The shell is of moderate thickness, and bears a flange at the posterior 

 half in some spores. Two pyriform polar capsules, frequently of slightly 

 different dimensions, are at the anterior part of the spore. No intercapsu- 

 lar appendix is present. When the spore is allowed to stand for 24 hours 



