THE MYXOSPORIDIA, OR PSOROSPEEMS OP FISHES. 169 



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



Siir line uonvelle espi;ce de psorospermic {Lithoojstia schneidei'i) parasite de 

 1' Echiiiocardium vordatum.; Coiniit. Rcud. Acad. Sci. Paris, 1876, Lxxxii, 

 pp. 1208-1210; transl. Aim. Mag. Nat. Hist., Loudon, 1876, xviii, pp. 

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

 SchnoLdcr's Tablettes Zoologiques (./(rfe Pleiffer, Die Protozoen als Krauk- 

 heitserreger, p. 49) ; ib. Pcrrier, 1893, Traite de Zool., p. 459. 

 Cyst unknown. 



Plasmodium. — Forinin.i>: sliining- black (pigmented) irregular masses. 

 Size varying- fiom that of a point to 10 mm. by 4 or o mm., aspect and 

 consistence similar to that of the myxomycete i)lasmodia5 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 si>ore. 

 The little groups then resemble colonies of FhujeUafa, 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 deri\red 

 from host. The amoebiie 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. — Fusiform, length 6 to 10 ju, breadth 1 to 2 /^. 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 filanu^nts (subse- 

 quently becoming 1, as above described) tangential to the shorter axis. 

 Contents of spores merely a granular protoplasm, or from 3 to falci- 

 form corpuscles in course of formation, arranged around a central resi- 

 dual mass, which latter is finally reduced to 2 or 3 strongly lefringent 

 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 thijs i)arasite in fossil Echinodermata. 



'I. e., the i>oitiou correspondiug to tlae "anterior pole' of a luyxosporidiau spore. 



