THE MYXOSPORIDIA, OR PSOROSPERMS OF FISHES. 83 



THE SPORE. 



The myxosporidian spore always consists of at least 3 structures, viz : 

 a shell, one or more capsules with filament, and the single mass of 

 sporoplasm. In Myxoholus (p. 207) there is also sometimes present a 

 fourth structure — the tail. 



Pfeififer^ regards the myxosporidian spore as the equivalent of the 

 individual falciform germs [sporozoites) of the Coccidia. 



The Shell. 



This was noticed by even the earliest observers, who commented upon 

 its most prominent features, viz : its extreme transparency and resist- 

 ance to the strongest chemical reagents. Creplin^ was the first to 

 observe the separation of the valves after prolonged immersion in 

 water. It is extremely probable that the shell substance is the same 

 throughout the whole group, as we find the constant shell characters 

 to be the micro-chemical ones, variation appearing to be rather struct- 

 ural than chemical. This substance is thin, very transparent, insolu- 

 ble in the strongest acids and alkalies in the cold, certainly in some, 

 and probably in most species destroyed by (soluble in?) concentrated 

 sulphuric acid at its boiling temperature;** usually with little affinity 

 for staining reagents. The shell i)ossesses a minute pore (or pores) 

 for the exit of the spiral filaments. 



Two types of shell are (provisionally at least) to be distinguished. 

 These are the bivalve shell, and a type in which no bivalve structure 

 has been detected. 



The first type comprises 2 subtypes, viz : (a) plane of junction of 

 valves coincident with the longitudinal plane; characteristic of Myxo- 

 holus; and (b) plane of junction of the valves perpendicular to the 

 longitudinal plane; characteristic of the Cystodiscidw and the Chloro- 

 myxidce. 



The second type is found in the Glugeidce and in Myxidium lieber- 

 Tciihnii. 



Tail. — Confined within and described under the genus Myxoholus 



(p. 207). 



Capsules and Filaments. 



morphology. 



Capsule. — Always pyriforra, consisting of a thick, elastic, brilliant, 

 ordinarily opaque wall encompassing a central cavity; wall drawn out 



' Die Protozoen als Krankheitserreger, 1891,2 ed., p. 8. 



2 Wiegmauu's Arcliiv. f. Naturgesch., 1842, i, p. 63. 



" Balbiani asserts (Journ. de Microgr., 1883, vii, p. 202) thatboiliug sulphuric acid 

 does not affect tlie shell. This Biitschli (Ztschr. f. wiss. Zool., 1881, xxxv, p. 634) 

 denies, stating that strong heating with sulphuric*acid destroys entirely the shell 

 substance. My own experience with several species tallies exactly with that of 

 Biitschli. 



