SPECIAL MORPHOLOGY AND TAXONOMY OF SPOROZOA 453 



that they are not formed as a result of fertilization, are the most 

 characteristic structures of the Myxosporidia and are much more 

 highly differentiated than are sporoblasts of the former group. 

 They conform to the same general plan of structure throughout but 

 differ in axial relations and in sculpturing, as well as in number and 

 time of appearance. The spore capsule always consists of two valves 

 which are independently developed and come together with a median 

 suture dividing the spore into right and left halves. In different 

 types the spores may be elongated in the plane of the suture or at 

 right angles to it. The polar capsules with their coiled threads 

 indicate what most authorities regard as the anterior end although 

 spores of the Myxidiidse have thread capsules at each end of the 

 elongated spore (Fig. 187). We agree with Kudo (1919) that the 

 axial nomenclature suggested by Davis (1917) is unnecessarily com- 

 plicated and that antero-posterior differentiation is characteristic 

 of the vast majority of these spores. Lateral processes, posterior 

 spines, and external sculpturing of various types distinguish the 

 different genera and species and afford a means of classification. In 

 this wefollow Kudo (1919) as follows: 



Sub-order 1. Eurysporea, Kudo (1919). 



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

 one polar capsule at each side of the plane and without "iodinophilous 

 vacuole." Coelozoic parasites for the most part, the great majority in 

 marine fish. A single spore (monosporous) , double spores (disporous) and 

 many spores (polysporous) formed by individuals. 



Family 1. Ceratomyiddee, Doflein (1899). The sole family with char- 

 acters of the sub-order. 



1. Genus Leptotheca, Thelohan (1895). Marine fish parasites; spore with 



hemispherical or rounded valves; disporous where known; 15 species. 



2. Genus Ceratomyxa, Thelohan (1892). Marine fish parasites; valves of 



spore extended into long lateral conical and hollow processes; sporo- 

 plasm asjamnetrically placed; monosporous, disporous and poly- 

 sporous; 35 species. 



3. Genus Myxoproteus, Doflein (1898) em. Davis (1917). Marine fish 



urinary bladder; spores more or less pyramidal; disporous; three 

 species. 



4. Genus Wardia, Kudo (1919). Tissue parasites of fresh-water fish and 



amphibia; spore an isosceles triangle with convex sides; surface of 

 spore with fine ridges with fringe of processes at the posterior end; 

 polysporous; 2 species. 



5. Genus Mitraspora, Fugita (1912) em. Kudo. Fresh-water fish kidney, 



spores spherical or ovoidal, valves longitudinally striated with or 

 without long, fine filaments projecting posteriorly in a row at right 

 angles to the sutural plane at the posterior end, disporous and 

 polysporous; 3 species. 



Sub-order 2. Sphserosporea, Kudo (1919). 



Spores spherical or subspherical with two to four polar capsules; sporo- 

 plasm without iodinophilous vacuole; monosporous, disporous and poly- 

 sporous; body cavity and tissues of fresh- and salt-water fish and amphibia. 



