AN ACHLYA LACKING SEXUAL REPRODUCTION 357 
descriptive or even misleading. Edson (2) for his most interesting 
new genus Rheosporangium describes a similar type of spore (p. 285) 
as "plano-convex or slightly concavo-convex, with a central vacuole, 
and on the flattened side a sinus from the bottom of which the two 
cilia of unequal length arise." The description and the accompanying 
figures agree in general with the writer's observation of this type of 
spore in Achlya, Thraustotheca, Dictyuchus, and other genera of the 
Saprolegniaceae. 
Upon emerging from the cysts the zoospores swim actively about 
for 'as long as thirty minutes if in pure water, and then round off, 
lose their cilia, and encyst (Fig. 4). These encysted zoospores ger- 
minate either directly or after a period of rest according as available 
nutriment is present or absent. Germination takes place by the out- 
growth of a tube (Fig. 5) which shows scanty development, or which 
ultimately forms an extensive mycelium, the amount of growth being 
proportionate to the amount of available nutriment. 
Resistant Spores.— \n the details of its life history as considered 
thus far, the fungus is a typical Achlya. The formation of a hollow 
sphere by the sporangiospores at liberation, the character of the 
zoospores which emerge, and the method of sporangium renewal are 
distinguishing characteristics of the genus. In its further develop- 
ment, however, the fungus differs from any Achlya hitherto recorded 
in that zoosporangium formation is normally followed by the produc- 
tion not of sexual organs, but of heavy-walled resistant spores of a very 
distinct type. Both in gross and in pure culture, formation of these 
resistant spores follows the production of zoosporangia with remarkable 
regularity. Resistant spores are produced exclusively, however, under 
the conditions found by Klebs (7) to inhibit the formation of zoo- 
sporangia, although favoring the development of "gemmae." Par- 
ticularly is this true of I percent agar solution. 
Although this Achlya is truly an aquatic fungus, these resistant 
spores are produced in culture not only in liquids but also aerially on 
solid media. In flask cultures on fairly dry cornmeal they are formed 
in especial abundance. When such a culture is inoculated with a 
bit of mycelium, a vigorous growth ensues, covering the surface of the 
medium from which innumerable stout hyphae with dense whitish 
content push up into the air. On examining such a culture with 
a binocular microscope after three or four weeks, large numbers of 
resistant spores can be seen especially around the edge of the culture. 
