THE MYXOSPORIDIA, OR PS0R08PERMS OF FISHES. 227 



MyxosporidUim.^ — Pfeiffer lias seen the exit of the sporoplasm. He 

 did not have the opportunity to cultivate the spores via the over- 

 hanging drop, but says such cultivation would be easy and would show 

 the stage at which infection occurs. He did not actually see the 

 myxosporidium penetrate the muscle cell, but he has found within that 

 cell all growth-stages of the myxosporidium. The elongate myxo- 

 sporidia often show, in their center, pansporoblasts containing well- 

 developed spores, while at the ends these structures are smaller and 

 contain only 1, 2, 4, or more nuclei. Tliis proves that, as in the Sareo- 

 sporidia (also with the tubes of Sygnathus a,nd,Jide Thelohan, with those 

 of Gottus Scorpio), growth takes place at the ends of the tubes. Have 

 these younger developmental stages originated from gerjns from the 

 interior of the large tube, do tliej- i^roceed from residual germs of the 

 first multiple infection, or. do they develop from newly immigrated 

 germs "? A positive answer can not yet be given, but in the barbel Pfeiffer 

 regards the second mode (viz, a supplementary outgrowtli from the 

 germs which penetrated en masse in the first infection) as the more 

 probable. In the myxosporidium tubes germs migrate from the center 

 to the circumference, where they find better food conditions and through 

 progressive division become new pansporoblasts (Sporenkugeln). The 

 cejiter of the cyst is also empty in the cysts of the sheep, those of 

 the tench's air bladder, and that of the kangaroo's intestine. When 

 the myxosporidia have attained a certain size, they are found free in 

 the interstices of the muscular fiber. When crowded, they fuse to an 

 irregular mass ; only at the edges are some unfused myxosj^oridia to be 

 seen. Hjematoidin crystals are found in the myxosporidium. 



Spore formation. — This appears in the smallest circular cysts with 16 

 to 20 germs; also in uniloculate elongate cysts thickly filled with 100 

 to 200 germs. In places large granule cells are imbedded in the muscu- 

 lar fiber. At another ( ? later) stage the dancing granules have vanished 

 and the contents of the cells have separated with 10 to 20 or more pale 

 globules one-tliird the size of the ripe germs. Also some fibrilloe show 

 in their interior well-developed spores, with capsules and nuclei, single 

 or in rank and file (? accident; 1 pressure on cover-glass). The possi- 

 bility of these must be admitted, yet the contents of the capsules 

 appeared to have been voided. 



Spore. — Lenticular or oval; length 12 /a, breadth 10 pi, thickness 6 jn 

 (Ludwig); bivalve, shell cavity containing sporoplasm and 2 capsules, 

 the latter extruding filaments under the influence of potassium hydrate 

 (Megniu); by glycerin (Pfeiffer). 



Have the Myxosporidia resting spores? Mega-, ajid micro-spores 

 (differing only in size) occui'; also defective spores with 1 capsule, 

 with caudiform appendages, or with a subrotund form (Pfeiffer). 



Habitat. — Encysted and free in muscles, mostly of belly and sides of 

 body (ne^'er elsewhere, the liver, spleen, ovary, eggs, and gills being 



I Description, Pfeiffer's {loc. cit., 2 ed., 1891, p. 106). 



