1 56 ILLINOIS BIOLOGICAL MONOGRAPHS [394 



11, 1918, until March 10, 1919, when it was killed, being then nearly 

 dead. The material was examined on March 15. A few isolated spores 

 occurred in the muscle of Notropis blennius (Homer Park, 111., November). 



Vegetative form: In and between the muscle bundles of the myotomes. 

 Size variable. Color opaque white under the dissecting microscope. 

 Smallest rounded ameboid forms with a single or numerous nuclei, in the 

 muscle bundle, have the size of from 10m to 30/i in greatest diameter 

 (Figs. 573 to 575). The largest form observed was 400/x by 120/*. Young 

 forms without any differentiated protoplasm, shows indistinct granular 

 and reticular structure with deeply staining spherical or ring-form chro- 

 matinic granules. The number of the nuclei increases with the growth of 

 the body. Larger form (Fig. 576), spindle shape, circular in cross-section, 

 lies with its long axis parallel to the muscle fibres. The protoplasm 

 vacuolated, contained mostly mature spores. Spores were also found in 

 the state of diffuse infiltration. Polysporous. 



Spore: Form somewhat variable. Typical form almost circular, 

 slightly pointed at the anterior end (Fig. 566) in front view; spindle shaped 

 in profile (Figs. 569 and 570). Sutural ridge marked. Shell uniformly 

 thick, usually exhibiting four triangular folds on the surface along the 

 posterior margin (Figs. 566, 568 and 571). No intercapsular appendix. 

 Two pyriform polar capsules are, as a rule, of the same size and form. 

 Frequent occurrence of the inequality of the polar capsules together with 

 abnormalities in the form of the spore, were noticed especially among 

 comparatively young spores. The granular sporoplasm, shows two spher- 

 ical nuclei when stained. The iodinophilous vacuole, spherical and 2/x in 

 average diameter, is deeply stained with Lugol's solution. Dimensions 

 of unstained preserved spores: length and breadth 9 to lO^u, thickness 

 6.5 to 7)Li, polar capsule 6 to 7.5/x by 2.5 to 3ju. 



MYXOBOLUS DISCREPANS nov. spec. 

 [Figs. 597 to 601] 



Habitat: Branchial lamellae of Carpiodes diformis; Salt Fork, Urbana, 

 U.S.A. (May). One fish caught, died (soon after the capture) two hours 

 before being fixed. Length 8.5cm. 



Vegetative form: The parasites formed numerous cysts on the branchial 

 lamellae. Cysts slightly yellowish white and mostly rounded or elongated 

 along the lamella, occur in groups, often occupying the entire lamella. 

 Infection was fairly heavy. Every gill arch harbored ten to twenty cysts 

 mostly on the outer surface. Size of the cyst varies, small rounded one 

 500/i in diameter up to elongated forms 2mm. by 0.5mm., the majority 

 being from 0.5 to 1mm. in diameter. The cyst is surrounded by a thin 

 connective tissue layer of the host. The protoplasm shows little dififeren- 



