THE MYXOSPORIDIA, OR PSOROSPERMS OF FISHES. 287 



Lenii spheres {sjwroblasts, .senK. strict.) which ultimately develop into 2 

 spores still contained within the pansporoblast membrane. 



Development of sporoblast to spore: The tate of the 3 uneleus-like 

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

 into the spore-'' nucleus.'' Tlie other two do not ^ (as would naturally 

 be supposed) develop into the capsules; on the contrary, the 2 nuclei 

 disaitpear, while the capsules appear in the protoplasm independently 

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

 within the pansporoblast 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 parrially disorganized shells. 



^ijore.— Transversely and unequally biconvex-lenticular; length, 5 /< 

 {jho'", Lieberkiihn; 4 to 6 /«, Thelohan); breadth, 20 /.i or less (Biits- 

 chli; 15 to 20 /f, 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 2; tilaments 2 to 3 times the breadth of tlie 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 lieberkiihnii does not contain a vacuole. This is a fact of 

 which I have assured myself many times. The dark streak shown iu Biitschli's 

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

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

 a single mass. 



Exit of sporoplasm (PfeitTer),— Easily observable by examination of 

 bladder-mucus 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 annrboidly 

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

 away. 



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

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

 contrary, he describes the process substantially as follows: 



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

 (heretf^fore, though thin and delicate, plainly perceptible), after a variable period, 

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



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

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



•2 Sometimes only 1 capsule at 1 "end," very rarely 2 capsules together in tlio 

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

 situated together at 1 "end" (Biitscbli). Balbiani iigures, beside the usual forms, 

 others with 2 capsules iu each wing. 



