The Naturalist. 



irregularly througli their substance. The filaments are without septa, 

 thus differing from Peronospora. The fungus appears to belong to 

 the genus AcJilya Nees. {Saprolegnia Kiitzing), which according to the 

 Micrographic Dictionary is to be found " growing parasitically upon 

 the bodies of dead flies lying in water, also upon fish, frogs, &c., and 

 in some cases upon decaying plants." The filaments vary in thickness 

 from yJ^Q-th to al^yth of an inch, being usually smallest where they 

 are closely crowded. With a good l" objective the granular matter 

 may be seen to circulate in the filaments, generally appearing to 

 •oscillate backwards and forwards in a given area, but occasionally 

 (when accumulating to form a fruit head) moving much more actively. 



When a filament is a few days old, the granular matter accumulates 

 towards the tip to such an extent as to give it a slightly clavate form. 

 A septum is then formed so as to enclose the granular matter, and 

 thus cut off the sporange in which the zoospores develop. A little 

 hooked tip is formed at the end of the sporange, and it is here that 

 it bursts when ripe. The spores do not take long to ripen, and then 

 the case bursts, and emits a mass of tiny globular cells containing 

 apparently only a few fine granules. For a few hours they remain 

 clustered together, and in the meantime develop a thin transparent 

 envelope which seems to be made only to shed again, for all at once 

 the envelope bursts, and an active zoospore escapes, which rushes in 

 and out of the field of the microscope with great activity. In this 

 state the zoospore is kidney-shaped, and has two cilia attached to the 

 concave side, by which it propels itself. In a few minutes, however, 

 the zoospore comes to a state of rest, resumes its original globular 

 form, the cilia drop off, and it secretes for itself another coat. In a 

 little while a prominence appears, which is gradually extended in the 

 form of a nearly transparent tube, until all the substance of the spore 

 is used up ; of course, if the spore could have settled on its food it 

 would have grown to reproduce itself as before. There will be from 

 50 to 100 zoospores in one fruit club, so that, considering the short 

 time they take to develop, there is no wonder the fungus so soon 

 covers the fish. As soon as one fruit club is done with, another 

 develops immediately beneath it, or on a lateral branch, and this 

 process is continued until all the granular matter in the cells is used 

 up. 



Besides this process of reproduction, however, there is another by 

 means of resting spores, which occurs less frequently, and generally 

 later on in the life of the fungus. The head containing the resting 

 spores is generally more or less globular in form, and the spores are 



