IX 
THE MYXOSPORIDIA, OR PSOROSPERMS OF FISHES. 2 
78. Myxobolus linearis Gurley, 1895. Pl. 36, fig. 2. 
(Psorosperm of Pimelodus sebe and of Platystoma fasciatum, Miller, 1841, Miiller’s 
Archiv., p. 489, pl. 16, fig. 10; ib., Miiller, 1843, Rayer’s Arch. de Méd. comp., 
pp. 228-229, pl. 9, fig. 10; ib., Robin, 1853, Hist. Nat. d. Végét. Parasites, p. 
300, pl. 14, fig. 11.) 
Myzxobolus linearis, Bull. U.S. Fish Com. for 1891, x1, p. 417; ib. of Pimelodes 
[error] etc., Braun, 1894, Centralbl. f. Bakt. u. Parasitenkde, xv, p. 87. 
Cyst not described; myxosporidium unknown. 
Spore.—Body very narrow; length,3 to 4 times breadth; capsules 
parallel-appressed, in contact along their entire length; tail simple, 
occasionally double. 
Habitat.—Cysts in membrane lining branchial cavity of Rhamdia sebee 
Cuy. & Val.; cysts on branchial lamelle of Pseudoplatystoma fasciatum 
L., from South American rivers. 
79. Myxobolus schizurus Gurley, 1893. Pl. 36, fig. 1. 
(Psorosperms of Hsox lucius, Miiller, 1841, Miiller’s Archiv., pp. 477-478, pl. 16, 
fig. 1; ib., Miiller, 1843, Rayer’s Archiv. de Méd. Comp., 1, pp. 219-222, 
pl. 9, fig. 1; ib., Dujardin, 1845, Hist. Nat. des Helminthes, pp. 648, 644; 
ib., Robin, 1853, Hist. Nat. des Végét. Parasites, p. 292, pl. 14, figs. 2, 3; 
ib., Lieberkiihn, 1854, Miiller’s Avchiv., p.5; ? ib., Thélohan, 1890, Compt. 
Rend. hebdom Soc, Biol. Paris, u, p. 604; ib., Weltner, 1892, Sitzgsber. 
Ges. Naturf. Freunde Berlin, pp. 29-35.) 
Myxobolus schizurus, Bull. U.S. Fish Com. for 1891, x1, p. 417; Wyxobolus schio- 
zurus [error] Braun, 1894, Centralbl. f. Bakt. u. Parasitenkde, xv, p. 87. 
Cyst.'—Whitish, 0-44 to 1:09 mm. (+-4’’) in diameter, membrane deli- 
cate, contents white, unaffected by water, consisting of finely granular 
matter and spores, the latter motionless. 
Myxosporidium unknown. 
Spore.—Body oval, double contoured, resembling and about the same 
size as the oval blood corpuscle of the fish; length 12 jy (0-0054/”’), 
breadth°6 «(7 4 Robin; 0-0026/’), thickness about one-half the breadth; 
border flattened-rotund, 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. Untailed 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. 
Habitat.—Encysted 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 North 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 mm.) and have thick walls. Under the 
microscope the entozoan can be seen moving with transverse wrinklings of its cyst. 
