DEVELOPMENT OF A MYXOSFORIDIAN 335 



was dried, then placed in absolute alcohol 15 to 30 minutes, 

 then washed in distilled water to remove any soluble substances 

 present in the urine which might interfere with the stain. After 

 washing the preparations were stained with Giemsa's stain over 

 night, decolorized with acetone and then mounted in neutral 

 balsam or damar. The latter was found to be preferable since 

 the stain was much more permanent than in balsam. 



For sectioning, the infected tissues were removed from fish 

 which had not been dead more than 5 to 10 minutes, placed in 

 Worcester's formol corrosive acetic fluid for several hours. 

 After washing and dehydrating in the usual manner the tissues 

 were imbedded in paraffine and sectioned. The sections were 

 stained with iron-hematoxylin and Congo red. This method 

 gave excellent results, both the nuclear and cytoplasmic struc- 

 tures being well preserved. Material killed in Schaudinn's 

 fluid and also in Hermann's fluid was inferior to that obtained 

 with Worcester's fluid. 



Most of the work was done at the Bureau of Fisheries Labora- 

 tory, Beaufort, N. C. during June, July and August, 1911 and 

 1912.^ 



III. DESCRIPTION OF TROPHOZOITES AND SPORULATION 

 I. Disporous form 



a. Living trophozoites. When the contents of the urinary 

 bladder are placed on the slide the trophozoites can usually be 

 found in large numbers. In most cases during June, July and 

 August both the younger stages previous to spore formation 

 and older trophozoites containing spores in all stages of develop- 

 ment, are abundant. 



The non-sporulating trophozoites are very distinctly amoeboid 

 but sluggish in their movements (fig. 1). When attached to 

 the lining of the bladder they are usually somewhat rounded 

 and closely applied to the free, rounded ends of the epithelial 

 cells, with one to several pseudopodia extending down between 



' Grateful acknowledgment is hereby made to the Bureau of Fisheries for the 

 opportunity to do this work. 



