THE MYXOSPORIDIA, OR PSOROSPERMS OF FISHES. 197 



l^pore formation. — Xumher of spores found in each sporigenons area 

 variable, always, however, more than 8, in which respect the present 

 species differs from the spores of Palcemon and CrangonJ Spores some- 

 times free, sometimes S tog«'ther in a common envelope, as in Palcemon.^ 



>Spore. — Size approaching and appearance the same as that of T. octo- 

 spora; ovoid, length 2 to 3 yu, with a clear vacuole in the larger end. 



Habitat. — Striated muscles of Astacua fluvlatilis (crayfish) from the 

 Department of Doubs, France; collected by M. Contejean in 1890. 



Pathological anatomy. — On section the muscles show nearly the same 

 appearance as in Paliemon and Crangon ; the fibrillre being separated by 

 parasitic masses, which in transverse sections appear as numerous 

 deeply stained punctules, and which in longitudinal sections assume the 

 appearance of irregular chains separating the fibrillar; the latter have 

 preserved their normal appearance, the striae beiug perfectly distinct. 



Xature. — The material was available only in alcohol, to which it had 

 been transferred from Fol's liquid. Owing to this, Hennegiiy and The- 

 lohan were unable to demonstrate the capsule with filament. The 

 similarity to the other species leads them, however, to believe it a 

 myxosporidian. 



Effects. — A notable diminution of muscular vigor was clearly estab- 

 lished with the myograph by M. Contejean. 



Epidemics. — In the Department of Doubs this disease has raged with 

 intensity among the crayfishes during several years and has caused the 

 death of a very great number of individuals. It seems now to have 

 disappeared. Moreover, this parasite can hardly be special to the 

 watercourses of Doubs, and, remembering the considerable mortality 

 caused by it in that Department, it is to be presumed that this hitherto 

 unknown organism has played a role in the genesis of the epidemic 

 which raged for several years in the East, and which has almost com- 

 pletely destroyed the crayfishes of that region. 



31. Thelohania octospora Henneguy, 1892. PI. 10, fig. 6; pi. 11, figs. 1-5. 



(Parasite of Palcvmon rectirostris and of P. serratus, Henneguy, 1888, M^m. 

 pnbli^es Soc. philomat. Paris I'Occas. Centen. Fondation, pp. 163-71; ii., 

 Tlielohan, 1891. Joum. de Microgr., xv, p. 146; ih. of P. rectirostris, 

 Th^lohan, 1891, Conipt. Rend, hebdom. Soc. Biol. Paris, iir, p. 28, name 

 only; ih., Th^lohan, 1891, Journ. de. Microgr., xv, pp. 146-7; ih., Pfeiffer, 

 I'^ni, Die Protozoen als Krankheitserreger, 2 ed., pp. 114-5; ih., Theloliau 

 and Henneguy, 1892, Coifipt. Rend, hebdom. Soc. Biol. Paris, iv, p. 586.) 



Thelohania octospora in Th^lohan, Bull. Soc. philomat. Paris, iv, pp. 165-6, 

 174, footnote; ih., Henneguy and Thdlohan, 1892, Annal. de Microgr., iv, 

 pp. 621-27, 629-032, pi. 4, figs. 1-8; ih. Gurlcy, 1893, Bull. U. S. Fish Cora, 

 for 1891, XI, p. 410; ih., Braun, 1893, Centralbl. f. Bakt. u. Parasitenkde, 



XIV, pp. 739^0; ih., Braun, 1894, Centralbl. f. Bakt. n. Parasitenkde, 



XV, p. 86. 



1 Henneguy and Th^lohan, Compt. Rend, hebdom. Soc. Biol. Paris, 1892, iv, p. 749. 

 *Henueguy and Th^lohau, 1892, Annal. de Microgr., ii, p. 638. 



