THE MYXOSPORIDIA, OR PSOROSPERMS OF FISHES. C7 
The extraneous pigment consists of hematoidin 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 Wyxidium lieber- 
kiihnit subpermanent bristle-like pseudopodia have also been observed 
(see p. 289). 
Ameboid movements.—These have been seen in a number of species.’ 
They are slow or active; sometimes absent, owing to the deleterious 
effect of so-called “indifferent” fluids. 
THE CYST. 
Encystment3—This—or at least the tissue-imbedding which is so 
termed (see below)—is the usual preliminary to reproduction in My.xo- 
bolus. Reproduction takes place without it, however, exceptionally 
in Myxobolus, and constantly in those forms inhabiting the cavities of 
the hollow organs.‘ 
MACROSCOPIC 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 miilleri, Biitschli?7 remarks 
that it differs from the type of membrane usual among the unicellular 
organisms (particularly the Gregarines) in its plasmatic nature, being 
1 In Mlle. Leclereq’s description of the Wyxosporidia (Bull. Soc. Belg. de Microsc., 
1890, xvi, p. 100) the erroneous statement is made that the Myxosporidia do not emit 
pseudopodia. 
2 Notably Myxobolus ellipsoides and Myxidium lieberkiihnii (pp. 222, 286). 
3 From the view that the Myxosporidia undergo a true (zoological) reproduction- 
encystment, Biitschli (Bronn’s Thier-Reich, 1882, 1, pp. 592, 593) dissents. 
4Cf. Lieberkiihn, 1854, Bull. Acad. Roy. Belg., xx1, pt. 2, p. 23; Thélohan, 1890, 
Annal. de Microgr., U1, pp. 197-198. 
5 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. 
7 Ztschr. f. wiss. Zool., 1881, xxxv, pp. 632,633; Bronn’s Thier-Reich, 1882, 1, pp. 
592, 593. 
