THE MYXOSPORIDIA, OR PSOROSPERMS OF FISHES. 185 
largest kinds of psorosperms. Several fish lost their cyst contents entirely. In an 
apparently half-empty cyst microscopic investigation showed the following objects: 
1. The largest form of the psorosperms, with a nucleus [Kern] of 0:005/’’ in 
diaineter and containing many of the smallest granules. 
2. The largest form of the psorosperms, with a much smaller ‘ nucleus,” namely, 
of 0-003/’’ in diameter, and filled with a much larger number of the smallest granules. 
3. Corpuscles of the same size with the same striking ‘‘nucleus,” with the same 
granules, but with a far less prominent surrounding membrane. 
4. Corpuscles of the same kind, but without demonstrable membrane, slowly pro- 
jecting a part of the body substance and again withdrawing it, whence resulted 
marked changes of form. 
[Page 356] 5. Corpuscles with all these characters; also provided with such a 
“nucleus,” but with a diameter twice as great. 
In order to determine whether the structures described occur in the organism of 
fishes and migrate in the spring to the external skin for the purpose of 
[Page 357] reproduction, I examined a series of the individual parts of the fish. In 
the blood I found moving colorless corpuscies, which agreed not with 
those of the fish, but much more closely with those destitute of grains and nuelei, 
originating from the psorosperms. And I also discovered in the kidneys of 
Gasterosteus receptacles with tailed psorosperms and the various developmental 
stages of the same, just as they occur in the gills of the pike. As the cysts 
often beset the skin of the stickleback in such great numbers that their sub- 
stance ‘forms a not inconsiderable fraction of that of the whole fish, it would 
have been difficult for them to have escaped me in my frequent examinations had 
they been present within the body of the fish. HEverything speaks much more 
for the view that certain aquatic animals attach themselves in the spring to the 
skin of the stickleback, surround themselves with a cyst membrane, and in repro- 
duction fall apart into the psorospermiform bodies. It is this animal which con- 
sists of a mucous substance, and which contains many scattered fat-like granules, 
and measures as much as 1’ Jong and about }/ thick. The fat-like granules are 
employed in reproduction; they break up first into smaller parts and then form 
with a certain quantity of the structureless substance a globule which already con- 
stitutes the embryo of the new being. This grows gradually, one of the granules 
progressively increases in size and the remainder vanish. Growth then continues 
for a long time, until granules show themselves anew, which increase at the expense 
of the nucleus; the heretofore plainly visible surrounding membrane becomes appa- 
rently thinner or vanishes entirely, and thus a body is formed consisting of a 
mucous mass containing many small scattered granules and a nucleus [Kern] 
only a little larger, a body capable of motion and growth. 
14. Genus et sp. incert. 
Psorosperms of Leuciscus dobula, Leydig, 1851, Miiller’s Archiv., p. 229. 
Oyst not mentioned. 
Myzxosporidium.—Two or three spores develop in each pansporoblast 
( Tochterblase). 
Spore.—Untailed. 
Habitat.—On Leuciscus (Squalius) cephalus (=dobula). 
15. Genus et sp.,incert. 
Spores of S@&valius cephalus, Schneider, 1875, Archiv. de Zool. Expér., Paris, Iv, 
pp. 548-9. 
Cyst and myxosporidium not mentioned. 
Spore.—Capsules 2, with very long filaments, extruded under action of 
glycerin. 
Habitat.—Air bladder of Leuciscus (Squalius) cephalus. 
