THE MYXOSPORIDIA, OR PSOROSPERIsrS OF FISHES. 



255 



78. Myxobolus linearis Gurley, 1893. PI. 36, fig. 2. 



(Psorcsperm of Fimelodus selxe and of Plafystomafasciatiim, Miiller, 1841, Miillcr's 

 Archiv., p. 489, pi. 16, fig. 10 ; U>., Miiller, 1843, Rayer's Arch, dc MM. comp., 

 pp. 228-229, pi. 9) fig. 10; ib., Robin, 1853, Hist. Nat. d. V<^-get. Parasites, p. 

 300, pi. 14, fig. 11.) 



Myxoholus linearis, Bull. U. S. Fish Com. for 1891, xi, p. 417; ib. of Pimelodea 

 [error] etc., Braim, 1894, Centralbl. f. Bakt. ii. Parasitenkde, xv, p. 87. 



Cyst not described; myxosporidiiim unknown. 



Sj)ore.— Body very narrow; ]onotli,3 to 4 times breadtli; capsules 

 parallel-appressed, in contact along their entire length; tail simple, 



occasionally double. 



Rabitaf.—Gjfits in membrane lining branchial cavity of Bhamdia sehoe 

 Cuv. & Val. ; cysts on branchial lamellse of F sen dopJaty stoma fasciatum 

 L., from South American rivers. 



79. Myxobolus schizurus Gurley, 1893. PI. 36, fig. 1. 



(Psorosperms of Esox hicius, Miiller, 1B41, Miiller's Archiv., pp. 477-478, pi. 16, 



fig. 1; ib., Miiller, 1843, Rayer's Archiv. de M6d. Comp., i, pp. 219-222, 



pi. 9, fig. 1; ib., Dujardiu, 184.5, Hist. Nat. des Helminthcs, pp. 643,644; 



ib., Rohtn, 1853, Hist. Nat. des V^g^t. Parasites, p. 292, pi. 14, figs. 2, 3; 



ib., Lieberkiihu, 1854, Miiller's Archiv., p. 5; ? ib., Th^lolian, 1890, Compt. 



Rend, hebdom Soc. Biol. Paris, ii, p. 604; ib., Weltner, 1892, Sitzgsber. 



Ges. Naturf. Freunde Berlin, pp. 29-35.) 

 Myxobolus schizurus, Bull. U. S. Fish Com. for 1891, xi, j). ill ; Myxobolus schio- 



zurus [error] Brauu, 1894, Centralbl. f. Bakt. u. Parasitenkde, xv, p. 87. 



Cyst.^— Whitish, 044 to 1-09 mm. (f4"0 in diameter, membrane deli- 

 cate, contents white, unaffected by water, consisting of finely granular 

 matter and spores, the latter motionless. 



IVIyxosporidium unknown. 



^^;ore.— Body oval, double contoured, resembling and about the same 

 size as the oval blood corpuscle of the fish; length 12 // (0-0054'"), 

 breadth 6 // (7 /< Eobin ; 0-0026'"), thickness about one-half the breadth; 

 border flattened-rotuud, marked by a ridge which extends forwards on 

 either side of the shell, projecting slightly in front; tail stout at origin, 

 attenuating gradually, 3 to 4 times length of the body, not articulated, 

 very frequently (probably as a rule) bifurcate at the tip, or for more 

 or less of its length. XJntailed forms very rare; capsules 2, of equal 

 size, always diverging posteriorly; remainder of shell cavity filled with 

 a transparent, rarely granular substance, differentiated by refraction 

 from the shell substance. 



Rabitat—Ency&ted in the orbit (never found elsewhere) in the cellular 

 tissue of the eye-muscles, in the sclerotic, and between the last and the 

 choroid of young Lucius lucius L. (pike) in May and June. Found in 

 only about 10 per cent of the fish examined. Miiller failed to find this 

 disease in the ISforth American pikes examined. 



1 These cysts are not to be confounded with similar white entozoan cysts. The 

 latter are of more frequent occurrence in the orbit than the myxosporidian cysts. 

 They are smaller in size (about 0-50 to 0-65 ram.) and have thick walls. Under the 

 microscope the entozoan can be seen moving with transverse wrinklings of its cj^st, 



