196 REPORT OF THE COMMISSIONER OF FISH AND FISHERIES. 



30. Thelohania contejeani Ilenueiruy, 1892. PI. 10, fi^s. 4, 5. 



'Parasite of crayfish, Iloimoirny and Thololiau, 1892, Compt. Rend, hobdom. 



Soc. Biol. Paris, iv, p. 719.) 

 TlieJohania contejeani, in Theloban, Bull. Soc. pbiloniat. Paris, iv, p. 174, foot- 

 note; U)., Hcnneguy and Tlielobau, 1892, Annal. tie Microgr., iv, pp. 

 637-9, pi. 4, figs. 26-7; ib., Branu, 1893, Centralbl. f. Bakt. u. Parasitenlcde, 



XIV, pp. 739-740; ib., Dubois' (Rapbad) 1893, Reeberebes de patbologie 

 coniparee sur la peste des ^crcvisses, Compt. Rend, bebdom. Soc. Biol. 

 Paris, V, pp. 158-9, figs. A,B; ib., Gnrley, 1893, Bull. U. S. Fisb Cora, for 

 1891, XI, p. 410; ib., Braun, 1894, Centralbl. f. Bakt. u. Parasiteukde, 



XV, p. 86; cf. La Maladie des I^crevisses en Alleniagne; Bull. Mensuel Soc. 

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

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



Cyst. — None. Parasitic mass producing au opacity of the affected 

 muscles, as in rahvmoii and Cranyon. Opacity more difficult of obser- 

 vation tbaii ill the last, ou account of the greater tliickness 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. 



' Tbis observer noted 2 (entirely distinct) parasites, viz: one wbicb Heuneguy 

 and Tb^loban pronounced a fungus, and one ■\vbicb 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 

 A'acuolate, escaping amuiboidly 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 months 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 aflluent of the 

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

 the pest. (3) The sources or Doye des NeyroUes 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 grow in nutritive fluids 

 caused Dubois to susj)ect it to be an animal (possibly a sporozoan) which ascended 

 the watercourse from the sea, perhaps brought by a fish. Tb61oban and llenneguy, 

 however, from an examination of bis 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 con ^e/eani.— 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 iu 

 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 iu the abdoment 



