THE MYXOSPORIDIA, OR PSOROSPERMS OF FISHES. 



241 



anterior end, but in the middle, and have tlieir axes parallel (fig. 3h). 



(2) Namerous mother vesicles [pansporoblasts] are seen containing 2 

 spores standing on edge, in contact, with their longitudinal planes 

 parallel; such spores show capsules in their interior in the usual place. 



(3) Eare cases occur (fig. Ge) where the mother vesicles contain 3 such 

 spores; these correspond to the rare cases in which the contents of the 

 spore consist of 3 x)arts. He concludes that the capsules are the germs 

 of new spores. 



Habitat. — Encysted in skin of the external or internal surface of the 

 opercles, in the rays of the branchial membrane, on upj^er surface of 

 head or on the fins of Stizostedion lucioperca {z=Lucioperca sandra), pike 

 perch, from German rivers and from the Don. Disease very frequent, 

 mostly in May and June. Miiller found it in from 20 to 25 per cent of 

 the young fishes examined. They were taken during the fii'st of the 

 winter. 

 62. Myxobolus globosus Gnrley, 1893. PL 28, figs. 1-3. 



Bull. U. S. Fish. Com. for 1891, xr, p. 415; ih., Braun, 1894, Centralbl. f. Bakt. 

 u. Parasitonkde, xv, p. 87. 



Cysts. — Varying from very minute to n maximum of 0-5 mm., elongate- 

 elliptic or rod-shaped, apparently (judging from ease of rupture) with 

 a very thin membrane; color, whitish; contents, spores. 



Myxosporidium unknown. 



Spore. — Globose, subcircular in outline, untailed; length, 7 orSyu; 

 breadth, 6 or 7/^; thickness, oia. Shell substance thin, very trans- 

 parent, composed of 2 valves (sui)erior and inferior in position), which 

 present a heavy ridge whose width nearly equals one-third of the thick- 

 ness of the spore. Valves equally and very convex oti their external 

 surfaces, appearing symmetrical on either side of the ridge. Oaijsules, 2, 

 of equal size, rather strongly diverging; capsular index somewhat more 

 than 0-50. Xuclei 3 or 4, viz: the 2 j^ericornual and 1 or 2 others, the 

 latter the usual and presumably the fully developed condition (see p. 

 92). Vacuole present. Owing to the great convexity of the sporoplasm 

 surface and the great thickness of its substance, it is not so clearly 

 outlined as usual. 



Habitat. — Encysted on the branchial lamelli© of Erimyzon sucetta 

 oblongus Lac. { = Catostomiis tuberculatus Le Sueur'), chub sucker. 



This species was found upon fishes from the first 3 localities; on those 

 from the fourth none were detected. 



The following is the record of fishes examined: 



TJ. S. Nat. 

 Mus. No. 



20.523 



2557.3 

 20105 



Locality. 



Date. 



Kinston, N. C 



Columbia, S. C \ Mar. 21, 1880 



Tributaries Fox Eivor, j 



Mi.ssi.s.sippi i 



Neai Pi<Tiiiont (?Pier- 



pou t) , N. Y 



Collector. 



J. W. Milner. 

 Marshall McDonald. 



S. F. Baird. 

 S. F. Baird. 



' Fide Jordan & Drayton, Bull. 12, U. S. Nat. Mus., pp. 100, 145; var. obJong us , fide 

 Prof. B. W. Evermann. 

 FC 16 



