234 
AMERICAN JOURNAL OF BOTANY 
[Vol. 8 
dish is literally covered by a thin layer of such spores and an equal number 
of empty spore-capsules. In some cases the contents of the spores were 
seen emerging, but so slow did this process appear to be that none were 
ever observed to swim away in the second swarming stage. On the other 
hand, a great many spores whose structure indicated that they were the 
end product of the first swarming stage were seen germinating by germ 
tubes, which eventually became slightly branched by short outgrowths. 
This is not uncommon in other species of the family. By transferring these 
empty capsules along with germinated and ungerminated spores to a slide 
and adding chlor-zinc iodide, no immediate reaction occurred, although a 
mature oogonium in the mount took a deep stain. On adding to this a 
rather strong iodine solution (in potassium iodide), the characteristic color 
for fungus cellulose appeared. The walls of the empty capsules, of the 
spores, and of the germinating threads, were definitely stained. The 
spores, during the period after the first swarming stage until they germinated, 
became more and more vacuolate. The scanty food supply demands that 
the germination tubes draw upon the protoplasmic content of the spore, and 
eventually doubtless they will perish, thread and spore. Although several 
weeks had elapsed since the first spores had germinated, no sign of sporan- 
gial formation at the end of the germination filaments was ever noted, 
although this occurs frequently in other species when food supply is lacking 
in the solution, and is perhaps to be found as a specific characteristic of 
certain species under other conditions. 
We may now turn to the reactions of this species under certain definite 
conditions. The description so far is that of its ''normal" behavior on a 
sterile house-fly in sterile conductivity water of high purity. If grown on 
fruit-flies (Drosophila), the rapidity with which the stages of its develop- 
ment follow one another is quite marked. The sporangia appear many 
hours earlier after exposure of the flies to the zoospores, and sexual repro- 
duction is several days ahead of the time for cultures on the house-fly. 
The food is more rapidly diffused and exhausted. 
In a solution of haemoglobin 0.05 percent -f KNO3 o.i percent, four 
days old, at the temperature mentioned before, the culture is found to 
have developed very abundant oogonial initials, arranged in torulose 
series as shown in figure 10, a, h (Plate XIV), and in some cases the terminal 
oogonium has already formed oospheres. The latter tend to be more 
numerous in each oogonium than is the case in fly cultures. At this same 
time the house-fly was densely covered with short, straight hyphae, nearly 
all bearing sporangia, mature or maturing or with sporangial initials. 
After ten days in this solution the earlier series had produced oospheres and 
some oospores, but those developed later showed signs of abnormality and 
disintegration. 
In a solution (always with conductivity water) of haemoglobin 0.05 
percent, in this case with an addition of 0.12 percent levulose, a culture 
