188 REPORT OF THE COMMISSIONER OF FISH AND FISHERIES. 



seen in way of further divisiou), the cell-uucleiis being as yet unaltered. 

 With continually progressing division, both of the myxosporidium and 

 the cell nuclei, and with progressive growth of the cell body, the origi 

 nally simple cell metamorphoses itself into a jilasmodium. Thus a 

 young Plasmodium was seen in which 1 of the 2 daughter nuclei o'' 

 the host-cell had fallen apart into 3 granddaughter nuclei, wiiile tin 

 myxosporidian nuclei had in the same time increased much more. In 

 the next developmental steps of the Plasmodium the number of the nuclei 

 increases very rapidly, and with such increase their energy becomes 

 exhausted; the nucleoli vanish and the nuclear reticulum appears as a 

 fine-grained granulation. Finally, the nuclear membrane shrinks and 

 assumes an irregular contour. The cell nuclei then soon entirely vanish 

 and we get a plasmode in whicli only myxosporidium nuclei are found 



With age the myxosporidia become displaced from the funicle and 

 occupy the whole cavity. The zooid, thus become a myxosporidium- 

 fdled tube, closed at both ends. At this time the increasing mutual pres- 

 sure produced by the continually growing myxosporidia results in their 

 fusion to large plasmodes. Further growth produces rupture of the 

 wall of tlie zooid and the myxosporidia come directly into contact with 

 its chitinous investment. 



The morphological characters of the adult myxosporidium are here 

 interpolated. 



Myxosporidium f {structure of adult). — NakedjUiembraneless, amoeboid- 

 variable, size 20 to 200 /^; form varying greatly with age, the youngest 

 being globular, the older ones oval or lobulated from adaptation to 

 external pressure-conditions. Ectoplasm perfectly transparent and 

 hyaline. Nuclei very numerous, consisting of clear round vesicles 

 showing in the fresh state round nucleoli. Applied against the out- 

 side of (never within) each nucleolus is a small glittering globule. 

 Pseudopodia formed by the ectoplasm, very fine, delicate and hair- 

 like, ordinarily confined to a part and seldom covering the whole sur- 

 face, often also forming small ramified tufts. Korotnefi' was unable to 

 state whether the pseudopodia serve for attachment, but with the young 

 myxosiioridia the fixation to the funicle appeared really to occur through 

 these structures. 



Probably the direct influence of the water is injurious to them, and 

 occasions a falling apart of the plasmodes and a freeing of the spores, 

 which then fill the spongy chitin-masses of the atro])liied colony. In 

 this state the spores remain the whole winter, and in April follows, prob- 

 ably, the infection of the young AhyoncUa (just out of the statoblast) by 

 the amoeba-brood from the spores. 



The time of the appearance of the myxosporidia corresponds with the 

 development of the sx^ermatoblasts, which ordinarily begins (around 

 Moscow) at the end of May, and the number of parasitic individuals 

 increases pari passu with that of the spermatoblasts. While at the 



