286 REPORT OF THE COMMISSIONER OF FISH AND FISHERIES. 
both varieties may be retracted and again extruded; some of these 
processes are, however, optical illusions, being views in optical section 
of transverse ectoplasmic folds (Biitschli; Pfeiffer). 
Ameceboid movements!: Slow, well seen when examined in the urine 
of the fish; absent (from rapid death of myxosporidium) in water and 
many “indifferent” fluids, e. g., egg-albumen solution. Best seen in 
pike’s urine at 24° C.; the ectoplasm executes very extensiveamceboid 
movements, wrinklings, and foldings (Pfeiffer). 
Spore formation.2—Not confined to adult forms, but found in myxo- 
sporidia of all sizes. Thus few-spored large, and many-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 place by the differentiation within the myxoplasm of a 
number of small, clear, transparent plasma-spheres ( pansporoblasts), 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- 
1! Gabriel (loc. cit.) gives a very detailed description of these movements, concluding 
that they are so complex and peculiar as to find no parallel with the Gregarines, and 
none appears admissible with the psendopodial movements of the Protozoa. Special 
emphasis is placed on the presence in the myxoplasm of a “‘thread-drawing” (Faden- 
ziehenden) substance, capable of emitting pseudopodioid processes, but incapable of 
retracting them. This, Gabriel asserts, finds a parallel only inmyxomycete plasmodes, 
of which it is an exclusive feature. Biitschli (1881, p. 640) has, however, observed 
the retraction of these processes. 
2 Description Biitschli’s, unless otherwise stated. 
3Pfeiffer 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 Gabriel 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 
sporigenous vacuoles being regarded as polysporogenetic centers strongly contrasted 
with the monosporogenetic centers of the Gregarines. 
4 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). 
