THE MYXOSPORIDIA, OR PSOROSPERMS OP FISPIES. 77 



The extraneous pigment consists of htematoidin crystals, whose 

 origin, mode of occurrence, etc., are discussed elsewhere (p. 285). 



Pseudopodia.^ — Usually blunt, simple or lobed ectoplasmic processes, 

 involving the endoplasm only when very large. In Myxidium lieher- 

 Mihnii subpermanent bristle-like pseudopodia have also been observed 

 (see p. 285). 



Amoeboid movements. — These have been seen in a number of species.^ 

 They are slower active; sometimes absent, owing to the deleterious 

 effect of so-called "indifferent" Huids. 



THE CYST. 



Encystment? — This — or at least the tissue-imbedding which is so 

 termed (see below) — is the usual preliminary to reproduction in Myxo- 

 holus. Reproduction takes place without it, however, exceptionally 

 in Myxoholus, and constantly in those forms inhabiting the cavities of 

 the hollow organs.* 



MACROSCOPIC APPEAKANCES. 



The most striking feature of the myxosporidiau cyst is the invariaUe 

 ahscncc of pigmentation. It is always of a cream- white color.^ In size 

 it varies within very wide limits, from a fraction of a inillimeter to 

 clusters of several centimeters in length. Shape also extremely variable^ 

 mostly spherical to fusiform. Usually it is easily detachable from its 

 place in the tissues. The cyst contents are always millcy or cream3^ 

 usually fluid, sometimes fiom defuiiency of water, caseous, and consist 

 of spores and more or less " granular matter." 



MICROSCOPIC APPEARANCES. 



Cyst memhrane. — In harmony with his view of the nature of the con- 

 tents of the Olugea anomala cyst, Gluge^ regarded the cyst membrane 

 as formed by the " solidification of an albuminous matter " of the host. 



Concerning this structure in Myxoholus milUeri, Biitschli^ remarks 

 that it differs from the type of membrane usual among the unicellular 

 organisms (particularly the Gregariues) in its plasmatic nature, being 



1 In Mile. Leclercq'a description of the ^ryxosporidia (Bull. Soc. Belg. de Microsc., 

 1890, XVI, p. 100) the erroueous statement is made that the Myxosporidia do not emit 

 pseudopodia. 



* Notably Ali/xohohts elUpsoides and Myxidium lieherkiihnii (pp. 222, 286). 



3 From the view that the Myxosporidia undergo a true (zoological) reproduction- 

 encystment, Biitschli (Bronn's Thier-Reieh, 1882, i, pp. 592, .593) dissents. 



"Cf. Liebcrkiihu, 1854, Bull. Acad. Roy. Belg., xxi, pt. 2, p. 23; Thdlolian, 1890, 

 Annal. de Microgr., ii, pp. 197-198. 



5 Of course not all white (nonpigmented) cysts are myxosporidiau. Some Trema- 

 todes occur in similar cysts, though they seem more usually to excite the deposition 

 of pigment. 



« Bull. Acad. Roy. Belg., 1838, v, p. 775. 



' Ztschr. f. wiss. Zool., 1881, xxxv, pp. 632;633; Bronn's Thier-Reich, 1882, i, pp. 

 592, 593. 



