244 KEPORT OF.THE COMMISSIONER OF FISH AND FISHERIES. 



(yellow perch) iu German rivers aud in the Irtisch (Miiller). Scales 

 (Lieberkiihn; Bessels). Disease not common. 



BemarJiS. — Bessels's form seems probably referable here, as he speaks 

 of having observed the longitudinal si)litting into 2 symmetrical halves 

 of an ellipsoid form. 



67. Myxobolus sp. incert. PI. 29, fig. 8. 



Psorosperms of Leitciscus rntilus, v. d. Borue, 1886, Handb. d. Fiaclizucbt u. 

 Fiscberei, p. 211, fig. 215. 



Ko description. 



Habitat. — On Leuciscus rutilus L. 



68. Myxobolus ?? zschokkei Gmley, 1893. PI. 31, fig. 1, 



(Psorosperms of Coregonus fera, Zscbokke, 1884, Arcbiv.de Biol., V, pp. 234-5, 

 pi. 10, fig. 16; ih., Liutou, 1891, Bull. U. S. Fisb Coin, for 1889, ix, p. 101.) 

 Myxobolus ?f zschokkei, Bull. U. S. Fisb Com. for 1891, xi, p. 416. 



Cyst. — Oval, white, size varying from that of a small ])ea to that of 

 a large nut; multiple, sometimes as many as 30 on one fish, the largest 

 usually situated in dorsal muscles; cyst membrane thick, very resist- 

 ant, without apparent structure; contents a milky fluid, occasionally a 

 caseous mass, coagulable by alcohol. 



Myxosjioridium unknown. 



Spore. — I quote in substance Zschokke's (description: 



Body lenticular or oval, a little wider in front tban bebind ; often bearing in front 

 a blunt 'prolongation; posteriorly one distingnisbes 2 '' tails" (queues), 6 to 8 times 

 longer tban tbe body, attenuating posteriorly, curved aud undulating ; tbe number 

 of 2 "tails" is constant; at tbe pole opposite to the "tails" are 2 oval, tr.ius- 

 parent anteriorly-converging vesicles; one sometimes sees, bowever, an extremely 

 fine canal extending from tbe posterior end of eacb vesicle to tbe base of tbe corre- 

 sjiouding "tail"; tbe vesicles tben probably play bere also tbe role of receptacles for 

 tbe "tails." Round refractile globules are also seen at tbe bases of tbe vesicles ; tbe 

 remainder of tbe body is filled by a homogeneous plasmic mass, which frequently 

 contracts to the center of the body cavity, forming a clearly distinct roiind or oval 

 mass. 



Habitat. — Encysted in the subcutaneous and superficial intermuscular 

 tissue of Corcgonus /era. Observed during April and May. Disease 

 stated by fishermen to be of very frequent occurrence. 



Effects. — The skin is irregularly swollen and the scales fall easily. 

 As to myxosporidiosis of Coregonus, see also p. 233. 



This form is a very puzzling one. As appears from the above 

 description and from the figure (pi. 31, fig. 1), the 2 'structures, called 

 by Zschokke "tails" {queues), are seen at one end, and at the opposite 

 end are 2 structures (the " vesicles" of the above description) approxim- 

 ating to the position of and presenting somewhat tlie appearance usual 

 to the capsules, and Zschokke considers them to be the capsules. 

 They converge, as do the capsules of most species, toward the end of 

 the spore, at or near which they are situated, and they diverge in the 

 opposite direction. From these facts one would be inclined to pro- 

 nounce this end (viz, the one at which these " vesicles " are placed and 

 toward which they converge) the anterior, and the opposite one (the 



