THE MYXOSPOHlDtA, OU PSOROSPERMS OF FISHES. l67 



Vauiety 3. — (Robin's plate 15, iigs. 3; 5a, I; 8.) 



Microscopic. — Cells regularly or irregularly ovoid, a little smaller tlian 

 those of the first variety, brownish yellow, presenting a peculiarity 

 found in no animal cell, viz, a round opercle.^ Cells unaffected by 

 acetic and nitric acids, and by ammonia. 



Macroscopic. — Colonies of variety 3, consisting of small lenticular, or 

 irregular brown or white masses scattered here and there at the base 

 of or below the lobes, and especially over the submucous surface of 

 the parasitic convoluted-strtng mass. 



(1) Brownish masses. — 2 to 4 mm. thick, composed of masses or 

 colonies of irregular, cupped, operculate cells, the whole enveloped by 

 a layer of cellular tissue containing very fine capillaries. Masses some- 

 times sufficiently numerous to color quite an area of the mucosa black- 

 ish brown. Further, when the convoluted-string mass is absent, brown 

 bodies may occur in the same situation. These bodies are ordinarily 

 accompanied by small peasized, whitish corpuscles, composed of round 

 granules measuring about 020 mm., formed of strongly united fibers of 

 cellular tissue wound around a small transparent, apparently calcareous, 

 body, it contains in the center 1 to 8 or 12 cells, furnished with an 

 opercle similar to that above described. 



(2) Whitish masses. — Composed of grains formed of 2, 3, 4, or 12 

 (rarely 1) cells, surrounded by a thick cellular tissue layer, the fibers of 

 which are strongly united by amorphous finely granular matter, the 

 whole forming rather hard, white, spherical or ovoid grains, ^ to ^ mm. 

 in size, often clearer in the center. 



Calcareous granules forming an oval or circular mass (fig. 5) with 

 sharply defined borders (the latter sometimes split); granules forming 

 whitish, more or less flattened, friable, irregularly lobulated, pea-sized 

 miliary masses. Granular mass destitute of vascularity, the vessels 

 being confined to the tissue sheath. 



Some masses are hard, yellowish white, of variable form, composed 

 of operculate cells, calcareous granules, and a great number of very 

 large, quadrilateral or rhomboidal, tabular crystals, the latter often 

 piled up, insoluble in acetic acid, in which only the calcareous granules 

 disengage some bullte of gas. Calcareous granules also occur without 

 crystals, being in this case whiter and less yellowish. 



The convoluted string {cordon enroule). — As described above, the cells 

 of varieties 1 and 2 form continuous (endless) cylindrical filaments, 

 those of variety 1 farming yellow filaments, those of variety 2 forming 

 white filaments. The convoluted string is usually^ formed of G of these 



' Robin gives the size of the opercle as 0'06 mm., but as he says the cells are smaller 

 than those of the firstvarietj^ (whose length is 0-027 mm.) this must be an error, pos- 

 sibly for 0'006 mm. 



2 Sometimes, however, only 2 filaments (instead of 6) are present, viz, 1 large 

 yellow filament (instead of 2), and 1 (not 4) thin white filament. Also (very rarely) 

 the convoluted string contains only 1 (instead of 6) white filament (variety 2) and 

 2 or 3 successive enveloping sheaths. 



