Minnesota Plant Diseases. 



FIG. 33. A spore-case of fish- 

 mold showing escaping swim- 

 ming spores; each of the 

 spores is provided with two 

 swimming lashes which whip 

 about in the water and propel 

 the spores. Highly magnified. 

 After Zopf. 



attack healthy fish unless perhaps 



through the respiratory system, but 



succeed if the fish are in some way in- 



jured, for instance at points where the 



scales have been rubbed off. When 



once the parasites are established they 



gradually spread over the body of 



the fish and ultimately cause its death. 



The fungus produces an enormous 



number of spores which are for the 



most part furnished with whip-like 



lashes for propelling purposes. Oc- 



casionally these fish molds cause epi- 



demics and vast numbers of fishes 



may then succumb. The occurrence 



of several such epidemics is known. 



These fungi are very often the cause of 



the death of fish in aquaria such as 



common gold fish. The danger from 



such fungi can be lessened by keeping 



the aquaria scrupulously clean so as 



to furnish little chance for the sapro- 



phytic existence of the fungus. The 



infected fish should be removed as 



soon as possible to prevent the forma- 



tion of more spores. The injuries of 



these fungi are not confined to the 



fish in lakes and streams but are 



sometimes a cause of great loss in the 



fish hatcheries where the eggs may be 



attacked. Some of the bread mold 



allies are also known as inhabitors of 



fish eggs. On the Amphibia, the 



frogs and their relatives, few fungi 



have been found. In this state mud 



puppies have been observed, which 



have been killed by certain fish molds. 



The fungus appeared on an apparent- 



ly healthy mud puppy as a thin filmy 



spot which rapidly grew larger, coa- 



lescing with other spots until the ani- 



