118 ILLINOIS BIOLOGICAL MONOGRAPHS [356 



Remarks: Two species of the genus Myxidium were reported to occur 

 in chelonian hosts; i.e., M. danilewskyi (page 109) and M. mackiei (page 

 112). The former differs from the present form in having an elongated 

 vegetative form which is greenish in color, and in having spores of different 

 shape, dimensions and structure, not to speak of the difference of the 

 host. The latter resembles closely to the species under consideration in 

 dimensions of the spores, but differences in the trophozoite and in the 

 structure of the spore do not allow one to consider two forms as identical. 

 The species is therefore treated as new. 



Genus SPHAEROMYXA Thelohan 

 1892 Sphaeromyxa Th61ohan 1892a : 1091-1093 



The characters of the genus are described on page 58. 

 Type species: Sphaeromyxa balbianii Thelohan. 



SPHAEROMYXA BALBIANII Thelohan 



[Figs. 296 to 307] 



1892 Sphaeromyxa balbianii Thelohan 1892a : 1091-1093 



1895 Sphaeromyxa balbianii Thelohan 1895 : 342 



1912 Sphaeromyxa balbianii Paris! 1912 : 288 



1916 Sphaeromyxa balbianii Georgevitch 1916 : 92-93 



1917 Sphaeromyxa balbianii Davis 1917 : 235-236 



Habitat: Gall-bladder of Motella tricirrata Bl., M. maculata Risso., 

 Cepola rubescens L., Clupea pilchardus, Siphostoma floridae, S. louisianae; 

 Roscoff (September), Concarneau, Marseille, Banyuls, Napoli (Septem- 

 ber), Beaufort (June to August). 



Vegetative form: Flattened leaf-like or disc-fcJrm, reaching 3 to 4mm. 

 in diameter. Often forms spherical with opaque appearance. The proto- 

 plasm is distinctly differentiated into endoplasm and ectoplasm. Ecto- 

 plasm forms rounded lobes which exhibit slow movements and show a clear 

 radially striated structure in sections. Endoplasm reticular, contains 

 nuclei, young and mature spores and fat globules. Each pansporoblast 

 develops two spores. Polysporous. 



Davis mentions that the largest form he observed was 900^t in diameter. 



Georgevitch recognized a large number of small trophozoites which were 

 formed by repeated plasmotomous multiplication. 



Spore: Fusiform, with truncate ends. Shell longitudinally striated. 

 One polar capsule at each end. Polar filament is wound around an imagi- 

 nary axis perpendicular to the longitudinal axis of the spore. When 

 extruded, the polar filament is seen as a short, conical and hollow thread- 

 like structure. Sporoplasm finely granular with two nuclei. Dimensions: 

 length 15/x, width 5)U, length of polar filament IS^t. 



