THE MYXOSPORIDIA, OR PSOROSPERMS OF FISHES. 277 



87. Ceratomyxa sphaerulosa Tli61olian, 1892. PI. 41, fig. 4. 



Bull. Soc. pMlomat. Paris, iv, pp. 171-3, 175, fig. 1; i6. Tholohan, 1892, Compt. 

 Reud. Acad. Sci. Paris, cxv, pp. 961-2 ; ib. Gurley, 1893, Bull. U. S. Fish Com. 

 for 1891, XI, p. 420; ih. Brauu, 1893, Centralbl. f. Bakt. u. Parasitenkde, xiv, 

 pp. 738-9; ib. Brauu, 1894, Ceutralbl. f. Bakt. u. Parasiteukde, XV, p. 87. 



Cyst, none. 



Mi/xosporidium.—Sjyhericid or ovoid ; youngest stages exhibiting very 

 distinct amoiboid movements, colorless 5 older individuals yellowish, 

 presenting a very remarkable constitution. Ectoplasm thin, emitting 

 lobed pseudopodia, with very slow movements. Endoplasm appearing 

 riddled with small (3 or 4 //) clear spheres between which lies a gray- 

 ish, finely granular plasma. Spheres often exhibiting, grouped at their 

 center, a variable number (most frequently 5 or 6) of small yellow, brown, 

 or greenish granules which resist nitric acid and potassium hydrate 

 longer than the gpheres which envelop them. Th^lohau was unable to 

 express any opinion as to the nature of the spheres, which, he remarks, 

 constitute one of the most remarkable peculiarities of this species. 



Spore formatmi.—E-cich myxosporidium forms at the most 2 spores; 

 never more. Solid distal portion of valve folded back along the pos- 

 terior border during development. Thdlohan notes the similarity in this 

 respect to the development in the tailed Myxoholus species (see p. 248) 

 and says that the anterior convexity of the curve presented by the long 

 (transverse) axis seems the effect of this primitive arrangement. 



^jjore.— Transversely extended, symmetrically (or subsymmetrically) 

 double scalene- triangular ; length, 8 to 10 or 12 yu; breadth, 90 to 100 /^.» 

 Shell bivalve; valves right and left; symmetrical or subsymmetrical ; 

 shape of each valve hollow-conical, with the distal extremity solid for a 

 variable distance; valves united along the cone bases, a slender ridge 

 marking their line of junction. The shell cavity thus consisting of 2 

 (lateral) halves, one of which is always occupied by a variable number 

 of small very pale masses whose exact nature is unknown, but which 

 seem to represent the residue of capsule formation. 



Sporoplasm.—Goiii^tantlj situated in the other half of the shell cav- 

 ity, of which it occupies only a relatively very small portion; finely 

 granular; no iodinophile vacuole. 



Capsules.— T^o, the largest known, filament very clearly seen, coiled; 

 extrusion easily produced by potassium hydrate or ether, each capsule 

 presenting as a rule a special opening placed ou one side of the suture. 



Eahitat.— Gall bladder (free floating in bile) of Galeus tnustelus 

 {=Mustelus vulgaris) smooth dogfish and of Galeorhinus galeus { = Galeus 

 canis) taken at VaMry-au Caux, by Balbiani, in August, 1891. 



1 Th^loliau gives tlie dimensions reversed (i. c, as length 100, breadth 8 to 10 or 

 12 n) but this is of courso a wrong orientation. Similarly with other species. 



