WATER MOLD (SAPROLEGNIA) 
353 
which are not known to have a life history of the type character- 
istic of either of the other subdivisions. 
Their life histories so 
far as they are known are imperfect. 
Phycomycetes (Alga-like Fungi) 
This group, as their name suggests, resembles the Algae, but it 
is a large assemblage of plants which vary widely in both struc- 
ture and habit. Some of them live 
in the water and have zodéspores 
and sex organs similar to those of 
the Green Algae, while some have 
lost their water habits and nearly 
all of their algal features. There 
are three principal orders — Water 
Molds (Saprolegniales), Downy 
Mildews (Peronosporales), and 
True Molds (Mucorales). 
Water Molds (Saprolegniales) .— 
These are the Fungi showing closest 
affinities with the Algae. In fact, 
if some of them had chlorophyll, 
they could scarcely be told from 
some of the Green Algae. They 
live in the water where they feed 
upon the dead bodies of insects, 
fish, and tadpoles. Sometimes they 
attack living organisms, as the one 
called Saprolegnia illustrates. 
Water Mold (Saprolegnia). — 
There are several kinds of Water 
Molds, but the one called Sapro- 
legnia, shown in Figure 804, is a 
very common one. Although com- 
monly a saprophyte on the floating 
bodies of dead organisms, it often 
attacks and kills young fish that 
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ye 
Fie. 304. — A Water Mold 
(Saprolegnia). A, a fly affected 
with Saprolegnia. The fuzzy ap- 
pearance of the fly is due to nu- 
merous hyphae which project from 
the body of the fly. B, tips of 
projecting hyphae which have 
formed zoésporangia. From the 
zoésporangium at the right the 
zoospores are escaping. C, a 
tip of a projecting hypha bearing 
an oégonium containing a number 
of eggs. D, an odgonium and an- 
theridium, the latter of which has 
pierced the wall of the odégonium 
and thereby enabled the sperms 
to reach the eggs. 
are confined in close quarters, on which account it is some- 
times very destructive in fish hatcheries. 
This Fungus, since 
it can live on both live and dead organisms, shows that there 
