Observations on SaprolegniecB. 25 



into it, and in two and one-half hours reached more than 

 half way to the opening (Fig. 7, PI. IV). A new sporangium 

 may be formed when, or soon before the filament has grown 

 through the old sac, or, as in some Saprolegnia since studied, 

 the filament may produce even a greater growth after than it 

 had made before the formation of the first sporangium. I 

 found a form growing on some very small bull-heads, which 

 after the first sporangium had developed, sent out, in many 

 cases noticed, a very extended and branching growth. They 

 were specimens preserved for study by being placed in a cell 

 and kept irrigated.^ 



The form just referred to as growing upon small specimens 

 of fish, and of which I was enabled to study out the parthe- 

 nogenetic forms, was peculiar in having the zoospores differ- 

 ing greatly in size, for, in the same sporangium, it varied 

 from .01 mm. to .021 mm. in diameter, the sporangia averag- 

 ing about .04 mm., and the filament .025 mm. in size. There 

 were also invariably a few zoospores remaining in the old 

 sac after it had opened, the cause of which was that a large 

 zoospore was unable to pass through the opening, thus keep- 

 ing back all the remaining zoospores until they had settled 

 down to the spherical form. The new filament is always con- 

 stricted where it passes the opening of the sac, showing that 

 it thus entirely closed it, holding the zoospores in a pouch 

 on the side of the filament. The zoospores developed in each 

 case were much less numerous than I have seen in any other 

 specimens, there being from ten to eighteen in each sporan- 

 gium. In some of the sacs which had been opened but a short 

 time, there was an infusorian nearly twice the size of the 

 largest zoospore. They must have passed in through the 

 openings of the sporangia, and were unable to make their 

 exit. 



In studying, and especially in growing these forms, one can 

 but notice the rapidity with which they develop, especially 

 under favorable conditions. Illustrating this point I introduce 

 the following table which embraces the results of timing the 



^I find that a very satisfactory way to keep growing specimens in a fresh condition under a cover 

 glass, is to place the slide by the side of a watch-glass of water, and, taking a short thread thor- 

 oughly moistened, place one end in the watch-glass, and apply the other closely to the edge of the 

 cover-glass. ]f not placed under abell jar evaporation will be sufficient to allow a supply of fresh 

 water. 



