3i6 RESEARCH IN PROTOZOOLOGY 



tween them seems to be too small for generic distinction. On the 

 other hand, the unicapsulated and bicapsulated Myxoholus should 

 better be separated into two different genera. 



5. Artificial cultivation. Although a number of investigators 

 have observed certain changes which myxosporidian spores under- 

 go when subjected to the digestive fluid of the host fish, no one has 

 succeeded in cultivating a myxosporidian in vitro. 



6. Problems concerning infection through the digestive tract. 

 Thelohan (1895) established the fact that the spores of Henneguya 

 psorospermica underwent certain changes when the gill-filaments 

 of infected perch containing the myxosporidian cysts were intro- 

 duced into the alimentary canal of another host fish, and considered 

 that the infection takes place through this system of the fish. 

 Subsequent observers confirmed this in various species of myxo- 



SPORIDIA. 



Auerbach (1909) undertook careful infection experiments with 

 Myxidimn bcrgcnse on young Gadits virens. He noted that young 

 amoebulee which emerged from the spores in the duodenum of the 

 host proceeded immediately up the bile duct, and after leading 

 intracellular life in the epithelium of the bladder or of the proximal 

 part of the duct, become extracellular stages which inhabited the 

 gall bladder. Erdmann (1912, 1917) fed the host fish the spores of 

 Chloromyxmn leydigi in gelatine capsules and found that two- 

 thirds of thirty-three fish thus fed became infected. In from three 

 to five days after the feeding, numerous trophozoites are said to 

 have appeared in the host's gall bladders. Davis (1916) observed 

 the emergence of the sporoplasm as an amoebula in five to fifteen 

 minutes from some of the spores of Sinuolinea dimorpha which 

 were subjected to the fluid taken from the pyloric ceca of the host 

 fish. Similar observation was recorded by Georgevitch (1917). 

 Kudo (1922) treated the spores of Leptothcca ohhnacheri with 

 the digestive fluid of the frog and observed the emergence of the 

 sporoplasms as amoebulse. Similar changes were noticed in the 

 spores which were introduced into the digestive tract of the host. 



The fact that prior to the emergence of the sporoplasm from 

 the spore the polar filaments are extruded from the capsules and 

 the spore itself, and shell-valves become opened along the sutural 

 plane, has been established in numerous species. As to the function 

 of the filament, very little is known at the present time. Leuckart 

 (1879) suggested that the polar filament is an attachment ap- 



