134 ILLINOIS BIOLOGICAL MONOGRAPHS [372 



Habitat: Muscle and connective tissue of kidney, spleen, intestine, 

 ovary, etc., of Barbus barbus L., and branchiae of B. fluviatilis Ag. and 

 B. plebejus Val.; Drac (June), Neckar, Prag, Milano. The cause of well 

 known ''Boil disease" (Beulenkrankheit) or Myxoboliasis tuberosa (Hofer) 

 of the barbels in European waters. Among many observers Keysselitz 

 made a thoro study of the parasite. His observations are as follows: The 

 disease occurs among the fish at any stage of growth. About 8% of the 

 fish, 7 to 15cm, long, caught in May and June between Conz and Trier 

 were infected with the parasites. The heaviest infection, however, occurs 

 among fish up to 40cm. in length; fish 50cm, long or larger show the tumors 

 caused by the parasites, rather rarely. Most of the fish die as the result 

 of the infection between the early part of April and the end of October. 

 The highest mortality is reached in the hottest months, i.e., July and 

 August. The temperature greatly affects the growth of the parasites. 

 Fish kept in the aquarium at a temperature of 25° C. or higher demon- 

 strate the growth of the boil in size daily. The boils are not noticed 

 during the winter and spring, they are formed from the early part of April 

 to the middle of October. 



Vegetative form: The parasites develop tumors of conspicuous size. 



Keysseltiz's observations are as follows: The tumor varies in size from 

 millet-grains to hen's eggs. Form spherical, oval or elongated. The 

 number of cysts on a single fish, is usually 3 to 4; often one, in some fish, 

 however, 23 were recognized on one fish. Usually tumors separated from 

 each other, rarely many forming one tumor. In one fish, 27cm. in length, 

 a tumor of 7cm. long, 4cm. broad and 3cm. thick, was observed in July. 

 The seat of infection is: the muscle of the body, muscle of pectoral and 

 anal fins, often in peritoneum and rarely in intestine. As the result of 

 breaking up of the cyst membrane, spores are also found in the testis, liver 

 and kidney. 



The tumor is composed of many vegetative forms, rounded, oval, 

 elongated, variously branched or flattened. Size reaches to 1.5mm. in 

 diameter. Protoplasm is usually differentiated into ectoplasm and endo- 

 plasm. The surface is not often smooth, but shows irregular outline. 

 Ectoplasm is seen often as a very thin, uniformly hyaline, indistinctly 

 granular or radially striated layer, giving the network-like appearance to 

 the surface of the body. Endoplasm, stained more deeply around the 

 peripheral part than other portion, shows a coarsely alveolar structure in 

 the central region. It contains vegetative nuclei, developmental stages of 

 propagative nuclei, granules, fat-like, often leucocytes and red blood 

 'corpuscles. The leucocytes, uninuclear or multinuclear, were seen at the 

 periphery, apparently in the course of degeneration. Red blood corpuscles 

 were found, in section, inside of the apparently intact parasite. Each 

 pansporoblast develops into two spores. Polysporous. 



