178 ILLINOIS BIOLOGICAL MONOGRAPHS [416 



KEYS TO THE GENERA AND SPECIES OF MYXOSPORIDIA 



No key to the genera and species of Myxosporidia has been published 

 up to the present time. This is due of course to the difficulties which 

 accompany such an attempt. These difficulties lie chiefly in the incom- 

 pleteness of the observations and descriptions of the majority of the species 

 of Myxosporidia. 



The writer has attempted in the following pages to carry out this task. 

 The key is by no means complete, as is unavoidable in the present state of 

 knowledge concerning this particular group of the Protozoa. 



Altho the spore is the fundamental factor used in constructing this key, 

 it was necessary to refer also to some other secondary characters such as 

 vegetative form and habitat. 



Some authors are inclined to think that the difference in host species 

 gives an ample basis on which to record the parasite as a new species. In 

 some cases the parasite is specific in a certain host species while in other 

 cases a number of different host species are infected by one and the same 

 parasite. Therefore one can not lay much emphasis upon a difference of 

 hosts in fixing the identification of a Myxosporidian. 



KEY TO THE GENERA OF MYXOSPORIDIA 



1(6) Spore approximately spherical 



Suborder Sphaerosporea Kudo 1919 2 



2(3) Spore with four polar capsules 



Family Chloromyxidae Thdohan 1890 



Genus Chloromyxum Mingazzini 1890 (183) 



3( 2) Spore with two polar capsules • 



Family Sphaerosporidae Davis 1917 4 



4( 5) Sutural line of spore straight 



Genus Sphaerospora Thdohan 1892 (185) 



5( 4) Sutural line of spore sinuous 



Genus Sinuolinea Davis 1917 (186) 



6( 1) Spore not spherical 7 



7(16) Largest diameter of spore at right angles to sutural line; two polar capsules, one 

 on each side of sutural line 



Suborder Eurysporea Kudo 1919 



Family Ceratomyxidae Doflein 1899 / 8 



8(11) Shell-valves prolonged laterally 9 



9(10) Shell-valves hemispherical or rounded 



Genus Leptotheca Th^lohan 1895 (179) 



10( 9) Shell-valves conical; free end tapering to a more or less pointed end 



Genus Ceratomyxa Th61ohan 1892 (180) 



11(8) Shell- valves rather elongated; circular in cross-section 12 



12(13) Spore rounded oblong; shell longitudinally striated; polar capsules pyriform, with 

 or without long and fine posterior filaments 



Genus Mitraspora Fujita 1912 emend. Kudo 1919 (183) 



Numbers enclosed in parentheses refer to the page of the article on which is found the description of the species 

 named. 



