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THE MYXOSPORIDIA, OR PSOROSPERMS OF FISHES. 169 
2. Lithocystis schneideri Giard, 1876. Pl. 2, figs. 1, 2. 
Sur une nouvelle espece de psorospermie (Lithocystis schneideri) parasite de 
VY Echinocardium cordatum; Compt. Rend. Acad. Sci. Paris, 1876, LXXXxII, 
pp. 1208-1210; transl. Aun. Mag. Nat. Hist., London, 1876, Xv, pp. 
192-194; also see Biitschli, Bronn’s Thier-Reich, 1, pp. 590, 602; figured in 
Schneider’s Tablettes Zoologiques (fide Pfeiffer, Die Protozoen als Krank- 
heitserreger, p. 49); ib. Perrier, 1893, Traité de Zool., p. 459. 
Cyst unknown. 
Plasmodium.—Forming shining black (pigmented) irregular masses. 
Size varying from that of a point to 10 mm. by 4 or 5 mm., aspect and 
consistence similar to that of the myxomycete plasmodia; surface of 
mass showing hyaline cysts with a structureless membrane, 2 mm. or 
less in diameter, containing one or more, rarely several, white points 
(crystal masses) and spores, the latter arranged in an irregular sphere. 
Spores situated at the extremities of filaments, which radiate from a 
central point, at which is a nucleus of a yellowish substance. Hach 
spore is sustained by 2 filaments tangential to the extremities of its 
shorter axis. Wherever possible (principally in the larger cysts), the 
spores become, at maturity, so rearranged as to form a number of little 
groups; spores cohering by their previous peripherally-placed portions.' 
At the same time the two filaments become applied to each other so as 
to form a single tail like filament 3 or 4 times the length of the spore. 
The little groups then resemble colonies of Flagellata, but the tail-like 
filament remains motionless. The coherence of the spores is due to a 
secretion produced at the adhering ends of the spores. 
Crystals insoluble in acetic acid, soluble in nitric acid, broken up at 
maturity of cyst, forming a sort of network, which seems to function 
somewhat similarly to the capillitium of the Myxomycetes in the dissemi- 
nation of the spores. Pigment of plasmodium believed to be derived 
from host. The amcebze present in the fluid of the body cavity of the 
host are regarded as originating from the falciform corpuscles, which 
are seen to slowly lose their form, and Giard believes them to produce 
by their union and growth the plasmodia. 
Spores.—F usiform, length 6 to 10 y, breadth 1 to 2 4. Some cysts 
(apparently the smaller) produce microspores, others megaspores, both 
of which classes differ from the ordinary variety of spore mainly in 
being more inflated towards the middle. Spore with 2 filaments (subse- 
quently becoming 1, as above described) tangential to the shorter axis. 
Contents of spores merely a granular protoplasm, or from 3 to 6 falci- 
form corpuscles in course of formation, arranged around a central resi- 
dual mass, which latter is finally reduced to 2 or 3 strongly refringent 
granules, and may disappear at maturity. 
Effects —The parasite causes the formation of small nodosifies on 
the inner surface of the test, which may enable us to recognize the 
presence of this parasite in fossil Hchinodermata. 
1T, e., the portion corresponding to the ‘‘anterior pole” of a myxosporidian spore, 
