THE MYXOSPORIDIA, OR PSOROSPERMS OF ElSHES. 235 



resistant; contents whitisli, consisting- of spores, witli more or less 

 granular detritus. 



Spore. — Outline spatular, approacliing roundisli-oblong; untailed; 

 length 14 to 17 //, breadth 8-5 //, thickness 5 to 6 /v. 



Shell substance thin, almost perfectly transparent, insoluble in cold 

 and moderately warm concentrated sulj)huric acid, quickly destroyed 

 when heated with the concentrated acid to near its boiling jjoiut; 

 insoluble in concentrated solution of caustic potash, cold or hot. 

 Valves separating in sulphuric acid (cold, concentrated), equally con- 

 vex, the spore on transverse view appearing symmetrical on both 

 (superior and inferior) sides of the wide ridge. Greatest convexity of 

 valves well forward (at about the junction of the anterior with the 

 second fourth of the length;) ridge index nearly ^. 



Capsules 2, pyriforni, of equal size, containing a coiled filament visi- 

 ble (in iodine water) through the capsular walls; capsules drawn out 

 anteriorly into the ducts, orifice visible. Methj^l- green stains the 

 cai)sular walls bright green ; the filaments, sporoplasm, and shell not 

 at all. Under this treatment there are differentiated in the uniformly 

 bright green capsular walls several dark green granules. Sometimes 

 only 2 are seen, and these are then often situated approximately in the 

 long axis of the capsules. Other specimens are seen with 4 or 5, which 

 are usually arranged without ma.rked regularity, generally, however, 

 being collected near the center. Their nature is problematical. Their 

 presence, position, and numerical range appear to be constant. 



Sporoplasm: The outline was not accurately traced, but the results 

 obtained by staining, suggest that upon the superior surface it may 

 perhaps extend to the anterior end of the shell; upon the inferior sur- 

 face it only reaches the posterior ends of the capsules. Upon this 

 view of the relations, the capsules would indent the inferior surface of 

 the sporoplasm. A similar condition appears to have been observed 

 in other species (pi. 34, fig. M). It is obvious that between the greater 

 (but partial) anterior projection of the sporoplasm upon the superior 

 surface in M. macrurus, and its complete anterior extension upon one 

 surface in the present species, various transitions might occur, and I 

 believe tliat this greater anterior projection alTords, even in the absence 

 of valvular inequality, a criterion for the discrimination of the superior 

 from the inferior surface, the greater projection being always superior 

 and the capsules always more or less inferior. 



Nuclei: Besides the deeiny methyl-green staining bodies in tJie 

 capsular walls, 3 series of bodies, which have a constant position and 

 stain with both carmine and gentian violet, occur. Those forming the 

 first series have every appearance of being, and I believe are, nuclei. 

 The second and third series are much more dubious, for if all tlje 

 granule-like particles which stain with gentian violet are to be regarded 

 as nuclei, the number of the latter must be reckoned as 1 or 2 score. I 

 have, therefore, merely described the appearances presented by the 



