395] STUDIES ON MYXOSPORIDIA— KUDO • 157 



tiation. The ectoplasm is a rather narrow zone around the entire body 

 and the endoplasm is filled with various nuclei, several stages of developing 

 pansporoblasts, and mature spores. Each pansporoblast produces two 

 spores. Polysporous. 



Spore: Approximately circular with broad anterior and more or less 

 narrower posterior end in front view; broadly fusiform in profile. Shell 

 uniformly thin with 5 to 6 markings on the posterior margin. Two polar 

 capsules broadly oval and convergent, fill the anterior half of the spore. 

 A small triangular intercapsular appendix presents. Coiled polar filament 

 is fairly visible in vivo. The spores from the cysts which were fixed with 

 alcohol-acetic and preserved in 95 per cent alcohol, showed the extrusion 

 of the polar filament under the influence of potassium hydrate solution 

 (35 per cent) even after a considerable length of time as is shown in the 

 following: 



Material fixed on May 29. 



June 2; Extrusion took place in almost aU spores. 



June 10; Extrusion took place in almost all spores. 



June 26; Extrusion took place in almost all spores. 



July 28; Extrusion took place in almost all spores. 



August 29; Extrusion took place in numerous spores. 



September 29; Extrusion took place in about 70 per cent of the spores, some filaments 

 being rather short, and not fully extended. 



October 20; Extrusion took place in about 50 per cent of the spores, most filaments being 

 short, and not fuUy extended. 



Sporoplasm coarsely granular shows clearly two ring-form nuclei in 

 fresh preparations. Dimensions of preserved spores: length 11.4 to 

 13.5/x, breadth 9.5 to ll/x, thickness 8.5 to 9.5m, polar capsule 5.5 to 6ju 

 by 3.5 to 4m, length of polar filament 50 to 55^. 



Remarks: The present species differs from the hitherto known species. 

 Myxobolus lintoni (page 138) and Myxobolus orbiculatus (page 155) which 

 are the nearest to the present form, differ from Myxobolus discrepans in 

 the host, organ of infection, vegetative form and form and structure of 

 the spore. 



MYXOBOLUS MESENTERICUS nov. spec. 

 [Figs. 628 to 631] 



Habitat: In the mesentery, liver, spleen and wall of stomach, pyloric 

 coecum, intestine, and gall-bladder of Lepomis cyanellus; Crystal Lake, 

 Urbana, 111. (June and July). Out of thirty-six host fish, 10 cm. in average 

 length, seven were found to be infected. In every case, except one, the 

 mesentery was the main seat of infection, harboring conspicuous cysts. 

 The number of cysts found in the host body varied from three to seven. 

 The infected fish did not exhibit any recognizable pathological changes. 

 Other species of fish caught at the same time, were free from the infection. 



