724 OEDER: MYXOSPORIDIIDA 



of accessory appendages (Fig. 307). In Ceratomyxa there are lateral 

 appendages, in Myxoproteus anterior ones, in Wardia a posterior fringe, 

 in Mitraspora a posterior filament, in Hoferellus a posterior spine, and in 

 Henneguya a posterior tail-like process. The surface of the shell or valves 

 is smooth or marked with ridges. Within the shell are the polar capsules, 

 which in most cases are situated at the narrow anterior end of the spore. 

 In the Myxidiidse there is one at each end of the spore, while in a few 

 species of Wardia the polar capsules are central in position. Each polar 

 capsule is spherical or pyriform in shape, and opens to the exterior by a 

 separate pore which is at the anterior end of the spore except in the spores 

 of the Myxidiidse, in which no distinction between anterior and posterior 

 ends can be made. There are always two polar capsules in the spore, 

 except in Myxoholus, which has one, and Chloromyxum and Agarella, which 

 have four. 



Within each polar capsule is a coiled filament, which can be extruded 

 through its pore. The filament is coiled round the long axis of the spore, 

 except in Sphceromyxa, in which it is coiled round an axis at right angles to 

 this. The filament is long and thin in all forms except Sphceromyxa, in 

 which it is short, thick, and tapering. In addition to the polar capsules, 

 the spore contains the infecting agent in the form of a cytoplasmic body, 

 sometimes called the sporoplasm, containing usually two nuclei, and 

 frequently an iodophilic vacuole filled with glycogenic material. 



Subdivision of the Myxosporidiida. 



The following classification, taken from Kudo's monograph (1919) on 

 the Myxosporidiida (=Myxosporidia Biitschli, 1881), is based chiefly on 

 the characters of the spores (Fig. 306). It difiers in the inclusion of the 

 genus Agarella in the family Chloromyxidee. 



1. Sub-Order: Eurysporea Kudo, 1919. 

 Largest diameter of the spore at right angles to the sutural plane. 

 One polar capsule on each side of the plane. Sporoplasm with no iodino- 

 philous vacuole. Vegetative form found in body cavity (except in two 

 species). Great majority parasites of marine fish. Monosporous, disporous, 

 and polysporous. 



(1) Family: CERATOMYXiD.tE Doflein, 1899. 

 With the characters of the sub-order. 



Genus: Leptotheca Thelohan, 1895. 

 Shell valves of spore hemispherical or shortly rounded. Fifteen 

 species. Disporous (seven unknown). Fourteen species in body cavity, 

 one in tissue; all in marine fish. Type species: Leptotheca agilis Thelohan. 



