THE MYXOSPORIDIA, OR PSOEOSPERMS OP FISHES. 169 



2. Lithocystis schneideri Giard, 1876. PI. 2, figs. 1, 2. 



Sur uue uouvelle espece tie psorosperuiie {Lithocystis schneideri) parasite de 

 1' Echinocardium cordatum; Couipt. Reud. Acad. Sci. Paris, 1876, lxxxii, 

 pp. 1208-1210; trausl. Ann. Mag. Nat. Hist., London, 1876, xviii, pp. 

 192-194; also see Biitsclili, Bronn's Thier-Reich, i, pp. 590, 602; figured in 

 Schneider's Tablettes Zoologiques {fide Pfeifter, Die Protozoen als Krank- 

 heitserreger, p. 49) ; ib. Perrier, 1893, Traite 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 jilasmodia; 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. Each 

 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. 

 Tlie 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 §eems to function 

 somewhat similarly to the capillitium of the Myxomycetes in the dissemi- 

 nation of the spores. Pigment of Plasmodium believed to be deri\Aed 

 from host. The amoebae 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 jjroduce 

 by their union and growth the plasraodia. 



Spores. — Fusiform, length 6 to 10 pi, breadth 1 to 2 //. Some cysts 

 (apparently the smaller) produce microspores, others megaspores, both 

 of which classes differ from the ordinary variety of spore mainljMn 

 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 nodosities on 

 the inner surface of the test, which may enable us to recognize the 

 presence of this parasite in fossil Echinodermata. 



^I. e., the portion corresponding to the "anterior pole" of a myxosporidiau spore. 



