Ward. — Fish Parasites and Parasitic Diseases- 213 



Among the various groups of Sporozoa the Myxospo- 

 ridia are peculiarly characteristic fish parasites. Many of 

 them ( ccur generally throughout the organs of the fish, al- 

 though others confine their attacks to special organs or sys- 

 tems. These forms affect chiefly the skin of the fish, yet are 

 commonly found in the gills, forming numerous nodules on 

 the gill filaments. Other species inhabit the intestine or 

 liver, and give rise to general epidemics of the most serious 

 type. Two species among these, Myxobolns cyprini and 

 Myxobolus ffeifferi, give rise to two of the best known and 

 most dangerous fish epidemics of Europe: the carp pox and 

 the catfish boil diseases. Of a similar character is the nodu- 

 lar disease of minnow and stickleback. 



In 1894 (iurley published an extensive monograph on the 

 psorosperms of fishes, in which he listed, from various parts 

 of the world, 70 valid species and 26 doubtful forms. These 

 were obtained from 76 lost species. Only 9 species are listed 

 from North America and but 7 of these come from fresh- 

 water fishes. Exceedingly valuable tables on distribution and 

 systematic keys make the work generally useful. Of North 

 American species he says that Myxobolus oblongus Gurley 

 from the chub-sucker is numerous on fish from Mississippi 

 and rare on those from other localities. M. globosits was 

 found on the same host from North and South Carolina and 

 from Mississippi. .1/. transovalis was present rarely on 

 shiners from Virginia. .1/. monurus occurred on the pike- 

 perch from New Jersey and M. macrurus on a Texas min- 

 now. .1/. linearis was collected on the bullhead from Iowa. 

 This brief list shows at once a wide range both of localities 

 and hosts for the few parasitic species. These forms are. 

 however, not so rare here as this record would seem to indi- 

 cate. In conversation with various persons, I have learned 

 that such parasites are frequently met with, and in one case 

 at least have produced an epidemic at a hatchery. Unfor- 

 tunately it was impossible to secure material for study and 

 determination as the time had gone by and the species present 

 must remain undetermined. That other yet undescribed 



