248 REPORT OF THE COMMISSIONER OF FISH AND FISHERIES. 
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71. Myxobolus medius Thélohan, 1892. PI. 31, figs. 2-4. 
(Cf. tailed psorosperms of kidney of Gasterosteus aculeatus Lieberktihn, 1854, 
Miiller’s Archiv., 1854, p. 357 (see p. 185); myxosporidian spores of G. acule- 
atus and of G. pungitius, Thélohan, 1890, Annal. de Microgr., 11, pp. 198-200, 
209, 211, pl. 1, figs. 1, 18 (last fide Thélohan, letter); ib. Thélohan, 1890, 
Compt. Rend. hebdom. Soc. Biol. Paris, 1, p. 604.) 
Henneguya media Thélohan, 1892, Bull. Soe. philomat. Paris, rv, p. 176. 
Myxobolus medius Gurley, 1893, Bull. U. 8. Fish Com. for 1891, x1, p. 416. 
Henneguya media Braun, 1898, Centralbl. f. Bakt. u. Parasitenkde, xIv, p. 739. 
Myzxobolus medius Braun, 1894, Centralbl. f. Bakt. u. Parasitenkde, xv, p. 87. 
Cyst none; myxosporidium unknown. 
Spore formation.—Pansporoblast apparently monosporogenetic (see 
pl. 31, fig. 4, reproduction of Thélohan’s fig. 18). 
Spore.—Fusitform; length, 20 to 22 yu (Thélohan, 1892); total length, 
24 to 30 yw (ibid., 1890); shell striate; tail present, resembling especially 
that of M. psorospermicus, curved close against the body during 
development, straightening only after rupture of the pansporoblast 
membrane; nuclei unknown; vacuole present. 
Habitat—Renal tubules and ovary of Gasterosteus aculeatus L. 
(stickleback); renal tubules and ovary of Pygosteus pungitius (9-spined 
stickleback). 
Effects —The following probably apply to this species, to M. brevis, 
and to Chloromyxum elegans: 
Upon the kidney, Thélohan’s observations are as follows: 
The organ is often almost entirely invaded. Upon section one sees nearly all the 
tubes completely obstructed by psorospermic matter. The canaliculus invaded is 
dilated and attains relatively enormous proportions, the entire kidney being conse- 
quently enormously augmented in volume, and its function evidently must be almost 
completely abolished. A remarkable fact of this invasion of the renal canaliculi by 
the Myzxosporidia is the small amount of disorder that they occasion. Beyond the 
dilatation of the tubes one observes only a little augmentation of volume of the nuclei 
of the epithelium. The cells are otherwise respected, and I have never seen the 
protoplasm of the myxosporidium invade them or insinuate itself between them. 
This is due without doubt to the dilatability of the renal tubules. 
The following upon the ovary probably applies both to M. medius 
and to M. brevis: 
Upon sections of this organ one sees the connective tissue invaded by the plasmic 
masses, which separate its fasciw; certain invaded ovules have completely lost their 
normal aspect and present in their interior more or less confluent islets of psoro- 
spermic matter. 
72. Myxobolus creplini Gurley, 1893. PI. 32, figs. 1, 2. 
(Psorosperms of Acerina vulgaris, Creplin, 1842, Wiegm. Archiv. f. Naturgesch., 
1842, 1, pp. 61-3, pl. 1, figs. A-E; ib., Rayer, 1843, Rayer’s Archiv. de Méd. 
Comp, I, pp. 268-9; ib., Dujardin, 1845, Hist. Nat. d. Helminthes, p. 644; 
“tailed” psorosperm of Acerina Leydig, 1851, Miiller’s Archiv., p. 222; 
psorosperm of Acerina vulgaris Leuckart, 1852, Archiv. f. physiolog. 
Heilkde, X1, p. 486, fig. 21e; ib., Robin, 1853, Hist. Nat. de Végét. Parasites, 
pp. 312-14; spore of Acerina vulgaris, Weltner, 1892, Sitzgs—Ber. Ges. 
Naturf. Freunde, Berlin, 1892, pp. 29-31, 34). 
Myxobolus creplini, Bull. U. 8. Fish. Com. for 1891, x1, p. 418; ib., Braun, 1894, 
Centralbl. f. Bakt. u. Parasitenkde, xv, p. 87. 
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