THE MYXOSPORIDIA, OR PSOROSPERMS OF FISHES. 273 



92. Chloromyxum (Sphaerospora) dujardini Th^lohan, 1892. PL 40. fig.s. 4-7. 



Synonymyr. — The first 6 references in the table, except those to Dujar- 

 din and to Biitschli, represent the same form, the later being mere copies 

 of Miiller. The fusion of the form observed by Dujardin with that ob- 

 served by Miiller is on the authority of Thelohau, who states (letter to 

 the author, 1893) tliat he has observed his Myxosonia dnjardini upon both 

 Leuciseus rutilus and L. erythrophth/dmus, and that he believes that 

 Miiller's and Dujardin's figures represent the same species. Biitschli's 

 form is also probably referable here; size of the last, 0-40 mm. 



Concerning the form observed by him in Leuciseus rutilus, Miiller says : 



Once there was found on the psoudobranchias {Nebenlciemen) .amass of small yellow 

 cysts. The size of this mass was 4 lines. This time all the cysts contained elongate 

 capsules [spores] with pointed anterior and bluntly rounded posterior ends (fig. 4?;). 

 Ou the flat border the convex surfaces were exactly equal and the 2 diverging vesi- 

 cles were attached interiorly at their points. 



Thus this form was never found coexisting in the same cyst with 

 Myxoholus cycloides. Considering the great frequency of occurrence of 

 the latter species such coexistence would be exi:)ected if they were 

 merely diflerent forms of one species. Their persistent nonassociation 

 thus strongly reinforces the argument in favor of their specific distinct- 

 ness drawn from their different characters. 



Cyst not described. 



Myxosporidium. — Spores imbedded in and held together by an almost 

 diaphanous, ramified, glutinous mass, 1-25 to ] -50 mm. long, decompos- 

 able by water, analogous to the amcebai, apparently destitute of an 

 envelope (Dujardin). 



Spore. — Oval, pointed anteriorly, broadly rounded posteriorly, length, 

 10 to 12 n (0-0051" ' to 0-0054'"); breadth, 7 /i (0-0031'") untailed; cap- 

 sules 2, of equal size (Miiller). 



Habitat. — Encysted in the pseudobranchise of Leuciseus rutilus from 

 German rivers; branchial lamellae of Leuciseus [Seardinius) erythroph 

 thalmus from the Vilaiue, at Eennes, France, 

 F c 18 



