THE COMMON HOUSE-FLY. 153 
abdomen, and in a day or two after the whole will be found 
dried, and the surface of the wall or glass lightly covered: in 
a semi-circle, at about one-half to one inch from the fly’s ab- 
domen, with a cloud of whitish powder. This whitish, 
fatty substance is found on examination to consist of a vast 
number of short, erect filaments growing out from the body 
of the fly, between the rings. These flaments contain large 
oil-globules, often arranged in a row, and these having been 
mistaken for spores gave origin to the name of Sporendo- 
nema, applied to this fungus. Mr. Cohn has described its 
growth somewhat minutely and changed .the generic name 
to HLmpusa, or rather Lmpusina, the first of these names be- 
ing already appropriated. He states that the vesicle fila- 
ments terminate in the abdomen in a continuous, often 
branched tube and consist therefore of a single tubular cell. 
The upper free end, however, becomes cut off by a septum, 
and the terminal cell acquires a campanulate form and a 
dark color; when ripe it is thrown off with some force, and 
a number of these form the white cloud above mentioned. 
Fig. 127 shows these parasitic plants. You have all no 
doubt observed this halo or oriole surrounding a dead fly 
fastened to the window or looking-glass. 
“Mr. Cohn endeavored in vain to make these spores ger- 
minate; and nothing like them were found in the cavity of 
the abdomen of numerous flies in which the filaments were 
traced in their earlier stages. Mr. Griffith inclines to regard 
them as peridioles or spore-cases; or they may be stylo- 
spores, which after a stage of rest produce an intermediate 
mycelial structure, and then give birth to the ripe spores. 
‘When we turn our attention to the poor sufferer, we 
observe no outward signs of the disease in its early stage; 
yet watching carefully great numbers of flies we soon detect 
some that differ from the rest by a more erect abdomen and 
by their awkward way of walking. At first they are rest- 
Jess, constantly running and flying about; if the disease, 
however, grows worse, their motions become very sluggish, 
and if you approach them with your fingers they eitherijdo 
not fly away at all or in a very clumsy way, soon settling 
again. At last they are unable to walk more than a few 
