218 REPORT OF THE C0MM1;-SI0NER DE FISH AND FISHERIES. 



}r!/xosp()ri(UKm. — Myxosporidium nsunlly sliOAving no cloar diffeien- 

 tiatioii of ectoplasm and endoplasui except in thin sections, wliere certain 

 portions exhibit very phiinly a tolerably thick, graruule-free exterior 

 zone, possessing a great interest on acconut of its very distinct fine 

 radiate striation. Bndoplasm thickly stndded with very small bnt 

 distinct nuclei which in thin sections are, even in the fresh state, rather 

 .plainly visible as faint roundish corpuscles, in which dilute acetic acid 

 differentiates a dark somewhat granulated membrane, a small dark 

 nucleolus, and, sometimes quite clearly, fine nuclear threads radiating 

 from the nucleolus to the membrane. This structure, together with 

 their intense affinity for stains, jjermits no doubt as to their nuclear 

 nature. 



Spore formation.^ — This species never shows a paired spore-develop- 

 .ment, or a development within a pansporoblast (? ; see below), the 

 spores being directly imbedded in the endoplasm. These spores, how- 

 ever, show indications of a similarity in their development to the other 

 Myxo.sporidia in their origin from a trisegmented ("trinucleate") plasma- 

 globule, 2 of whose segments develop the capsules and the third the 

 sporoplasm. 



Development of spore."^ — In the myxosporidium, inclosed in a delicate 

 membrane, a^ number of mature spores are seen, many things pointing 

 to their origin from the proto])lasm. They always contain 3 pale, 

 almost spherical, but somewhat angular bodies. The membrane fre- 

 quently shows an excavation and an opening at one end. At this end 

 the 2 i)rotocysts are situated, the protosporoplasm being remote there- 

 from. Further observation shows the i)rotosporoplasm to develop into 

 the sporoplasm of the mature spore and the two protocysts to give 

 origin to the capsules. The latter structures develop witliin the proto- 

 cysts, the filament appearing first in the extruded condition, apparently 

 forming a prolongation of the capsular wall. 



Subsequently, in the light of his observations on the development of 

 Jfi/J7i<7mm ?ieier7cii/mn, Biitschli inclined to interpret thus : That the 3 

 spheres (viz, the 2 protocysts and the protosporoplasm) represent 

 not plasma-spheres but nuclei, the latter being, on this supposition, 

 imbedded in a plasma mass which he had failed to see, probably on 

 account of strong swellings and great transparency. 



The observations of Balbiani and of Thelohan, however, render it 

 almost certain that Biitschli's observations were accurate and that his 

 subsequent interpretation was erroneous (see also pp. 82, 223). Upon 

 this view the present species would seem to develop pansporoblasts, 

 each with a single spore. 



/Spor^.^-Lenticular-oval, anterior end sharpened, showing quite plainly 

 a shallow funnel-shaped depression; posterior end rounded ofl"; dimen- 

 sions 10 to 12 /^ by 9 to 11 yu. On vertical view, contour rather variable, 



1 Biitschli, 1882, Brouu's Thier-Reich, i, p. 597. 



'^Tiie description is Blitsclili's (Ztschr. f. wiss. Zool., 1881, xxxv, pp. G46-8). 



