322 GOLDSTEIN: RESTING SPORES OF EmMpusA MUSCAE 
various sorts. Apparently resting spores are not always formed, 
but their occurrence in different lots of material, collected in the 
fall and winter of 1921 and 1922, shows that they are by no 
means rare. 
The chief reason why investigators have commonly failed to 
find the resting spores is apparently their failure to examine old, 
dried up material, such as can be found attached to walls and 
windows throughout the winter. The resting spores are evi- 
dently most commonly, though not always, formed very late 
and as a final stage of the disease, after the body of the fly has 
begun to dry up. 
The evidence is clear that the resting spores I find belong to 
Empusa Muscae and not to Entomophthora americana or any of 
the other entomophthorous forms that are said to occur in the 
house fly. All the flies studied, fixed, and sectioned are typical 
house flies. The flies sectioned show no traces of other fungi. 
That the fungus is Empusa Muscae is definitely established 
by the fact that the conidia in all my sections which show them 
fully formed or in process of formation are the broad, multi- 
nucleated type characteristic of this species (Fic. 1). They do 
not resemble in the least the narrower and uninucleated conidia 
of Entomophthora americana. In none of my sections have I 
observed a single branching conidiophore. The conidiophores 
of E. americana are regularly branched. Many of the sections 
containing resting spores also show the multinucleated conidia 
and simple conidiophores of E. Muscae projecting between the 
abdominal segments. 
Finally the insects were all found attached by means of their 
proboscides and not by means of rhizoids appearing at other 
regions of the body, as is the case with the other entomophthorous 
forms that are said to occur upon the house fly. 
As described in the literature several forms of resting spores 
occur in the Entomophthoreae and they may be either sexual 
or asexual in origin. When they are of sexual origin, they are 
described as arising through the fusion of equal gametes or equal 
hyphal bodies. The terms encysted hyphal body, chlamydo- 
spore, and azygospore are used to designate resting spores of 
asexual origin. 
The term chlamydospore is properly used to designate a 
resting spore formed by the rounding up of portions of the pro- 
