THE MYXOSPORIDIA, OR PSOROSPERMS OF FISHES. 287 



liemisplieres {sporohlasts-^ sen-s. strict.) which ultimately develop into 2 

 spores still contained withiu the pansporoblast membrane. 



Develoj)nieut of sporoblast to spore: The fate of the 3 nucleus-like 

 bodies remains in doubt. The central one BUtschli observed to develop 

 into the spore-" nucleus." The other two do not ^ (as would naturally 

 be supposed) develop into the capsules; on -the contrary, the 3 nuclei 

 disappear, while the capsules appear in the protoplasm independently 

 of them. Gabriel sometimes observed the sporoblasts (i. e., spores still 

 within the i^ansporoblast membrane) to undergo a slow progressive con- 

 traction to a globular shape, showing their membrane (presumably the 

 future spore-shell) to be not yet rigid. A similar contraction was seen 

 by the same observer in spores with jiartially disorganized shells. 



Spore. — Transversely and unerpially biconvex-lenticular; length, 5 /^ 

 (too'"? Lieberkiihn; 4 to 6 //, Thelohan);- breadth, 20 /< or less (BUts- 

 chli ; 15 to 20 /;, Thelohan). Shell plainly visible, sharp contoured, 

 rather thick, frequently showing a delicate anteroposterior striation; 

 bivalve structure unknown, sulphuric acid producing no effect. Cap- 

 sules 1 in each wing-; filaments 2 to 3 times the breadth of the spore. 

 Sporoplasm almost completely filling the shell-cavity, extending even 

 to the wings, there surrounding, as a thin layer, the capsules, Nuclei, 

 2 {fide Thelohan, letter 1893), Concerning them and the vacuole-like 

 structure shown in Biitschli's figures, M. Thelohan writes : 



The spore of Myxidium HeherkUhnii does not contain a vacuole. This is a fact of 

 wliich I have assured myself many times. The dark streak shown in Biitschli's 

 figures belongs, without doubt, to the 2 nuclei of the plasmic mass which are often 

 ajjproximated, and, after the action of slightly elective stains, appear blended into 

 a single mass. 



Uxit of sporoplasm (Pfeiffer). — Easily observable by examination of 

 bladder-raucus in urine of pike at 24° C. After 4 to 12 hours a scat- 

 tered mass of burst shells are seen; also many spores not yet burst, 

 showing the contents much more plainly separated than in fresh speci- 

 mens. In some individuals the sporoplasm is seen to flow amoeboidly 

 out " between the shells" (which are peculiarly unraveled) and wander 

 away, 



Gabriel states that during the whole year that he studied this species 

 lie never saw the shell split to give exit to the sporoplasm. On the 

 contrary, lie describes the process substantially as follows : 



Shell undergoing a rather easily observable fluidiiication or resorption, its contour 

 (heretofore, though thin and delicate, plainly percej^tible), after a variable period, 

 entirely disappearing. Sometimes during the resorption stage, always by time of 



' On the contrary, Pfeiffer (Die Protozoen als Krankheitserreger, 1890, 1 ed., p. 98; 

 1891, 2 ed., p. 132), however, states that the capsules are formed from these 2 nuclei. 



'^Sometimes only 1 capsule at l"end,'Wery rarely 2 capsules together in the 

 center (Lieberkiihn). Rarely ventricose monstrosities are seen with 2 capsules 

 situated together at 1 "end" (Biitschli). Balbiaui figures, beside the usual forms, 

 others with 2 capsules in each wing. 



