THE MYXOSPORIDIA, OR PSOROSPERMS OF FISHES. 77 



The extraneous pigment consists of lisematoiclin crystals, whose 

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



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

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

 Mlknii subpermaueut bristle-like pseudopodia have also been observed 

 (see p. 285). 



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

 They are slow or active; sometimes absent, owing to the deleterious 

 effect of so-called ''indifferent" fluids. 



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 pUice without it, however, exceptionally 

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

 the hollow organs.* 



MACROSCOriC APPEARANCES. 



The most striking feature of the myxosporidian cyst is the invariable 

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

 it varies within very wide limits, from a fraction of a millimeter 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 milky or creamy, 

 usually fluid, sometimes from deficiency of water, caseous, and consist 

 of spores and more or less " granular matter." 



MICROSCOPIC APPEARANCES. 



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

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

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



Concerning this structure in Myxobolus mUlleri, Biitschli^ remarks 

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

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



' In Mile. Leclercq's description of the Mijxosporidia (Bnll. Soc. Belg. de Microsc, 

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

 pseudopodia. 



* Notably Mi/xobohis elUpsoides and Mijxidinm Ueherkiilmii (pp. 222, 286). 



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

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



^Cf. Lieberkiihn, 1854, Bull. Acad. Roy. Belg., xxi, pt. 2, p. 23; Th^lohan, 1890, 

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



^ Of course not all white (nonpigmented) cysts are myxosporidian. Some Trema- 

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

 of pigment. 



6 Bull. Acad. Roy. Belg., 1838, v, p^ 775. 



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

 592, 593. 



