86 ILLINOIS BIOLOGICAL MONOGRAPHS [324 



altho some contained the parasitic masses in the tissue. About the middle 

 of July, the parasite forms conspicuous cysts in the tissue thruout the 

 organ. The cyst may or may not be covered by a thick layer of connective 

 tissue from the host. Aside from this hypertrophy, the host did not show 

 any pathological change which could be recognized. 



Vegetative form: Youngest trophozoite found in the urinary tubule 

 is multinucleate, rounded, and of from 20 to SOn in diameter. The proto- 

 plasm is not differentiated, the entire body is finely granular or coarsely 

 reticular in structure. In the protoplasm are to be seen nuclei and sporo- 

 blasts at different stages of development. The union of two propagative 

 cells similar to that of Myxobolus toyamai produces a small body which 

 developes into a single sporoblast and ultimately into a single spore 

 (Figs. 605-613). In later stages, the trophozoite reaches a size of lOOfi 

 in diameter showing many stages of spore formation and mature spores, 

 surrounded by thick layers of connective tissue from the host. Poly- 

 sporous. 



Spore : Elongated oblong with pointed anterior and truncated posterior 

 extremities. The width is often greatest at the middle of the polar cap- 

 sules, the posterior portion is much narrower than the anterior. Nearly 

 circular in the cross-section thru the polar capsules. The shell is thin, 

 the sutural line being faintly marked in fresh state. It generally is 

 obliquely located in relation to the capsules. The shell also shows fine 

 longitudinal striations, 14 to 16 in number, on each valve. The sutural 

 line as well as the striations are best seen in spores stained with Heiden- 

 hain's iron hematoxylin. Two polar capsules elongated pyriform, mostly 

 equal in size, occupy the anterior half of the spore. Abnormal situations 

 of the polar capsules are sometimes observed (Fig. 619). The coiled polar 

 filament is faintly visible in fresh spores. It is spirally coiled along the 

 wall of the polar capsule without any central axis. This fact was clearly 

 observed in stained section as is shown in Figs. 620 and 621. The fila- 

 ment has seven or eight windings, thus agreeing with the actual length 

 of the extruded polar filament. The polar filament was extruded under 

 the action of potassium hydrate solution. The extrusion takes place 

 even in some spores which were treated with Schaudinn's fixative and 

 kept in 95 per cent alcohol for three months (see the similar observations 

 on Myxobolus discrepans on page 157). The sporoplasm is finely granular 

 and transparent. When stained, it shows two nuclei in the center or near 

 the posterior part of the body. Dimensions of preserved spores: length 

 15 to 17;ii, breadth 5 to 6/1, thickness 4.5 to 5.5m, polar capsule 7.5ai by 2n, 

 length of polar filament 40 to 50/i. 



Suborder SPHAEROSPOREA nom. nov. 

 The definition of the suborder is recorded on page 57. 



