MYXOSPORIDIA 317 



paratus. Biitschli (1882), Thelohan (1895), Doflein (1899) and 

 others have expressed similar views. A thorough comprehension 

 of the mechanism of extrusion and of significance awaits future 

 investigations. 



As to the further changes of amoebulai within the host body, our 

 knowledge is fragmentary, since there seems to be little convincing 

 experimental evidence. All authors seem to agree in maintaining 

 that the liberated amcebulse in some way penetrate the gut- 

 epithelium and enter blood or lymph vessels. With the circulation 

 of the blood or lymph, they are carried into specific sites of infec- 

 tion within the host body. In the case of myxosporidia inhabiting 

 the urinary bladder of the host, some investigators hold the view 

 that the amcebulse make their way to the bladder directly through 

 the ureter (Davis, 1916). No one has succeeded yet in tracing by 

 experimental methods the entire change — from the emergence of 

 the amoebulse up to their establishment in specific sites within the 

 host body. The factors involved in the germination of the sporo- 

 plasm and, further, the factors which delimit numerous species of 

 MYXOSPORIDIA to a limited specific site of infection in the host 

 body, if the amoebulse make their way passively with the blood or 

 lymph stream of the host, await future researches. 



7. Problems concerning other modes of infection. Although 

 there is at least one case of well-established "hereditary infection" 

 in MicROSPORiDiA (see p. 340), no myxosporidian has been seen to 

 infect the next generation of the host through the germ cells. That 

 this mode of infection may occur in myxosporidia is highly prob- 

 able in view of the fact that several species were found infecting 

 ovarian eggs of certain fish (Kudo, 1920). 



8. Viability of the myxosporidian spore. As to how long the 

 myxosporidian spore would live under various circumstances, we 

 know very little. In order to determine whether the spores are 

 alive or not, one has to depend upon feeding experiments with 

 the host fish, since even the emergence of the sporoplasm in the 

 digestive fluid does not necessarily indicate the capability of the 

 amoebula to invade the host's tissue or organs and establish an 

 infection. 



9. Behavior of the two nuclei of tJie sporoplasm prior to, at the 

 time of or shortly after the latter's emergence from the spore. In 

 the great majority of myxosporidia there is a single binucleated 

 sporoplasm in each spore. 



