196 REPORT OF THE COMMISSIONER OF FISH AND FISHERIES. 



30. Thelohania contejeani Henneguy, 1892. PI. 10, figs. 4, 5. 



'Parasite ofciayfish, Ilenuesny aud Th^lohan, 1892, Compt. Reud. licbdom. 



Soc. Biol. Paris, iv, p. 749.) 

 Thelohania contejeani, in Th^lohan, Bull. Soc. pliilomat. Paris, iv, p. 174, foot- 

 note; ih., Henneguy and Th61olian, 1892, Annal. de Microgr., iv, pp. 

 637-9, pi. 4, figs. 26-7; ih., Brauu, 1893, Ceutralbl. f. Bakt. u, Parasitenkde, 



XIV, pp. 739-740; ih., Dubois i (Rapbajl) 1893, Recherches de pathologie 

 couiparc^e sur la peste des ^crevisses, Compt. Rend, liebdom. Soc. Biol. 

 Paris, V, pp. 158-9, figs. A,B; ib., Gurley, 1893, Bull. U. S. Fish Com. for 

 1891, XI, p. 410; !&., Braun, 1894, Centralbl. f. Bakt. n. Parasitenkde, 



XV, p. 86; cf. La Maladio des ficrevisses en Allemagne; Bull. Mensuel Soc. 

 Nat. d'Acclimat. France, February, 1884, p. 200 (transl.. Bull. U. S. Fish 

 Com. for 1884, iv, pp. 299-302). 



Cyst. — ISToue. Parasitic mass producing- au opacity of the affected 

 muscles, as in Palmnon aud Crangon. Opacity more difficult of obser- 

 vatiou than in the last, on account of the greater thickness of the test; 

 easily detected, however, on the inferior surface of the abdomen. 



Adult. — In some places only spores are seen; in others small plasma- 

 spheres, containing a variable number of nuclei, occur. These are 

 evidently developmental stages, but a full series could not be found. 



' This observer noted 2 (entirely distinct) parasites, viz: one which Henneguy 

 and Th(51ohan pronounced a fungus, and one which he determined to be Thelohania 

 contejeani. 



1. The former he describes as follows : 



Spore. — Cellules elongate, ovoid, cylindrical, or strangulated toward the middle, 

 according to the degree of development. Shell double-contoured; protoplasm 

 vacuolate, escaping amoeboidly through a small lateral orifice. Spores apparently 

 not capable of growth in nutritive fluids. 



Habitat. — Confined to the intestinal canal of the diseased crayfishes. The observa- 

 tions were made in June and July (1892), the mouths of maximum severity of 

 the epidemic. 



Crayfish epidemic. — Causes: Alterations of streams by industrial or agricultural 

 products can have only a subordinate and local influence. 



Area invaded divisible into 3 zones: (1) Lake Mantua (and its outlet to the sea, 

 the river Ain) ; formerly renowned for its crayfishes, which constituted an important 

 revenue; now destitute of crayfishes. (2) The Merloz rivulet, an affluent of the 

 lake, containing sound and diseased crayfishes, the latter showing the symptoms of 

 the pest. (3) The sources or Doye des Neyrolles feeding the lake and the Merloz 

 rivulet, from which latter it is separated by a dam, above which all the crayfishes are 

 healthy. 



The stoppage of its advance by the dam and its inability to growiu nutritive fluids 

 caused Dubois to suspect it to be an animal fpossibly a sporozoan) which ascended 

 the watercourse from the sea, perhaps brought by a fish. Thdlohan and Henneguy, 

 however, from an examination of his material, believed the form to be a fungus. 



The Distome described by Baer in 1827 (when no epidemic existed), to which Harz 

 attributes the crayfish epidemic, was sought for in vain. 



2. Thelohania contejeani. — Feeding experiment: Sound crayfishes were isolated 

 in reservoirs and fed, some with butcher's meat, and others with the flesh of trout, 

 carp, pike, and roach. After three months those fed on roach showed parasites in 

 the abdominal muscles. This parasite was identical with Thelohania contejeani. 

 Dubois asks: Do relations exist between the parasite found in the muscles and the 

 intestines in October, and that found in July in the abdomen? 



