286 REPORT OF THE COMxMISSIONER OF FISH AND FISHERIES. 



both varieties may be retracted and again extruded; some of these 

 processes are, however, optical ilhisions, being views in optical section 

 of transverse ectoi^lasmic folds (Biitschli; Pfeiffer). 



Amoeboid movements^: Slow, well seen when examined in the nrine 

 of the fish; absent (from rapid death of myxosporidinoi) in water and 

 many "indifterent" flnids, e. g., egg- albumen solution. Best seen in 

 pike's urine at 24° C; the ectoplasm executes very extensive amoeboid 

 movements, w^rinkliugs, and foldings (Pfeiffer). 



Spore formation.'^ — Not confiued to adult forms, but found in myxo- 

 sporidia of all sizes. Thus few-spored large, and mauy-spored small 

 myxosporidia are often seen (Gabriel). This occurrence at different 

 times is explained by successive ripenings of the different individual 

 myxosporidia composing the plasmode. Small round myxosporidia not 

 yet entirely freed from the epithelial cell-remnants often contain 2 or 

 more spores (Pfeiffer). 



Pansporoblast formation: This, the first step toward spore for- 

 mation, takes i)lace by the differentiation within the myxoplasm of a 

 number of small, clear, transparent xdasma-spheres [pansiwroblasts), each 

 consisting of one of the many nuclei of the myxosporidium, together 

 • with a portion of the surrounding myxoplasm which it has attracted 

 to it. Sometimes early, and in all cases later, each pansporoblast is 

 surrounded by a thin dark membrane,^ and is found to contain a 

 number of nuclei, usually 6. 



Pansporoblast-segmentation: Subsequently, instead of the pansporo- 

 blast consisting, as originally, of the pansporoblast membrane contain- 

 ing a single (usually sexanucleate) plasma-sphere, it comes to consist 

 of the same membrane containing two "• (usually trinucleate) plasma- 



' Gabriel (loc. cit.) gives a very detailed description of these movomeuts, concluding 

 that they are so complex and peculiar as to find no parallel with the Gregariues, and 

 none ajjpears admissible ^vith the pseudopodial movements of the Protozoa. Special 

 emphasis is placed on the presence in the myxoplasm of a "thread-drawing" {Faden- 

 ziehe7iden) substance, capable of emiltinq lyseudopodioid processes, hut incapable of 

 retracting tliem. This, Gabriel asserts, finds a parallel only in myxomycete plasmodes, 

 of which it is an exclusive feature, Biitschli (1881, p. 640) has, however, observed 

 the retraction of these processes. 



-Description Biitschli's, unless otherwise stated. 



^Pfeifl'er confirms. Upon examining a myxosporidium in a dilute solution of 

 eosin, or other stain, the spores stain only after rupture (by pressure on cover-glass) 

 of this membrane. Gabriel dissents, regarding the pansporoblast as a " wall-less 

 vacuole, which first takes on the vesicular appearance described by Leydig at a 

 later stage." According to Gabi'iel the pansporoblast does not always persist to 

 maturity, so that in the later stages it may be vainly sought. Gabriel was unable 

 to trace a genetic relation between the ''granules" (? nuclei) of the myxosporidium 

 and the spores, whence he concluded that the latter originate by a process, not of 

 myxoplasmic integration but by one of secretion, the morphologic substratum of the 

 sporigeuous vacuoles being regarded as pohjsporogenetic centers strongly contrasted 

 with the monosporogenetic centers of the Gregarines. 



■• Spores in this species always developed in pairs (Biitschli). Spores not always, 

 though usually, developed in pairs; such paired development may be absent among 

 both developing and free spores (Gabriel). 



