310 RESEARCH IN PROTOZOOLOGY 



general infection, the myxosporidian invasion is manifested by the 

 presence of tumors, cysts or growths on them. The latter are 

 usually milky white and vary in size and form. A number of 

 species have been found to inhabit superficial parts of the integu- 

 ment, namely, on or under the scales. In such cases the size of 

 the myxosporidian body seems to be limited by that of the scale. 

 This is the case with Myxobolus squmnco which Keysselitz (1908) 

 found in the barbel. The writer has in his possession two speci- 

 mens of river-chub, Hybopsis kcntuckiensis, of Illinois, which 

 exhibit a similar condition. 



Myxosporidia are also frequent parasites in the tissues of vari- 

 ous internal organs of the host fish. They have been found in the 

 heart, swim-bladder, nervous system, connective and supporting 

 tissues, muscles, various parts and glands of the digestive system, 

 spleen, gonads, excretory system and mesentery. Here also, if the 

 myxosporidian infection is at an advanced stage, one will find 

 abnormal local enlargements or growths which are usually of 

 milky white coloration. 



The organ-cavity inhabiting forms (coelozoic myxosporidia) 

 are either freely suspended in the fluid or attached to the epithe- 

 lium of the organ. The gall-bladder is most frequently inhabited 

 by the species of genera Lcptothcca, Ceratomyxa, Chloromyxum, 

 Myxidium, Sphceroinyxa and Zschokkella. The uriniferous tubules 

 of the kidney and the urinary bladder are also frequently the 

 site of infection by coelozoic myxosporidia. Ordinarily no ex- 

 ternal changes accompany the presence of myxosporidia living in 

 the host's organ-cavity. There is no symptom by which one can 

 suspect a myxosporidian infection. But the gall bladder of Trutta 

 fario heavily infected by Chloromyxum tnittcu was noted by Leger 

 (1906) to be highly enlarged and appeared reddish yellow in color. 

 The adjacent organs were deeply stained by the bile. As a rule, 

 however, one has to subject the bile or the contents of the urinifer- 

 ous tubules of the kidney or of the urinary bladder to microscopi- 

 cal examination in order to find the organisms. 



As to the sources of material, the common fresh-water or marine 

 fishes should be examined. For coelozoic forms, their gall bladder, 

 kidney and urinary bladder must be examined. The kidneys of 

 Rana clamitans and R. pipicns harbor frequently Leptothcca 

 ohlmacheri (Kudo, 1922). For histozoic forms, various tissues 

 of the common fresh-water fishes should be examined. For further 



