THE MYXOSPORIDIA, OR PSOROSPERMS OF FISHES. 185 



larjifest kinds of psorosperras. Several fisli lost their cyst contents entirely. In an 

 apparently lialf-empty cyst microsciopie investigation showed the following ohjects: 



1. The largest form of the psorosperms, with a nnclens lEern~\ of 0*005''' in 

 diameter 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 lilled 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, slowh pro- 

 jecting a part of the body substance and again withdrawing it, whence resulteu 



marked changes of form. 

 [Page 356J 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 



hshes and migrate in the spring to the external skin for the purpose of 

 [Page 3.57] reproduction, I examined a series of the individual parts of the fish. In 



the blood I found moving colorless corpuscles, which agreed not with 

 those of the fish, bvit much more closely with those destitute of grains and nuclei, 

 originating from the psorosperms. And I also discovered in the kidneys of 

 Gasterosteits receptacles with tailed psorosperms and the various developmental 

 stages of the same, just as they occur in the gills of tlie 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 jiresent within the body of the fish. Everything 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 gi'anules, 

 and measures as much as 1'" long and about i'" 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 [A'crw] 

 only a little larger, a body capable of motion and growth. 



14. Genus et sp. incert. 



Psorosperms of Lcucinciis dohula, Leydig, 1851, Miil]ci''s Arcliiv., p. 229. 



Cyst not mentioned. 



Myxosporidium. — Two or tliree spores develop in each i)ansporoblast 

 [Toi'hteyhlase). 

 Spore. — Untailed. 

 Hahitaf. — On Leuciscus {Squalius) ceplialus {=dohula). 



15. Genus et sp..;lncert. 



Spores of Sif^toJius cephaUis, Schneider, 1875, Archiv. de Zool. Exjidr., 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) ceplialus. 



