304 RESEARCH IN PROTOZOOLOGY 



in reptiles and amphibians (Kudo, 1920). Every species of fish 

 seems to harbor one species or another of this particular group of 

 protozoa. As far as known, myxosporidia were found everywhere 

 in the world where microscopical examination of fishes has been 

 carried. On several occasions, they were discovered by workers 

 who were engaged in lines of research not connected with 

 MYXOSPORIDIA, and this brought out numerous incomplete and 

 confusing observations and descriptions concerning them. For- 

 tunately, in the past twenty years there have been a number of 

 zoologists who have devoted themselves to the study of these 

 organisms. 



A great majority of known myxosporidia have been observed 

 in the fishes of France, Germany, Italy, Switzerland, England, the 

 United States, Brazil, and Japan. It is hoped that re-examination 

 of long known but little understood species occurring in Europe 

 and America and further microscopical examination of fishes in 

 other parts of the world would not only add some more taxonomic 

 information, but also solve some of the problems set forth in the 

 following pages. 



CLASSIFICATION 



Thelohan (1892) was the first to establish a classification of 

 MYXOSPORIDIA. As uumerous new species were discovered and as 

 more information was added to the trophic phase of these 

 PROTOZOA, a number of investigators attempted to improve the 

 system. Auerbach (1910) gave an excellent summary of them. 

 The writer (Kudo, 1920) also considered the systems then known 

 and pointed out that "the suggestion as to the adoption of other 

 characters than the spore for the divisions of myxosporidia, pro- 

 posed by Awerinzew (1907, 1908), Auerbach (1910) and Davis 

 (1917), can only be applied in future. At the present time, the 

 characters concerning the vegetative form do not appear to afiford 

 a better and more natural basis for the classification of myx- 

 osporidia than those of the spore. Thus from the taxonomic 

 point of view the present situation does not seem to be much im- 

 proved as compared with that at the end of the last century." 



Unfortunately this still holds true. In the last ten years, no one 

 has undertaken to consider the system carefully, although Dunk- 

 erly (1925) made a brief remark with regard to the one the writer 

 set down (1920). Both Calkins (1926) and Wenyon (1926) 



