THE COMMON HOUSE-FLY. 153 



abdomen, and in a day or two after the whole wall 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 filaments contain large 

 oil-globules, often arranged in a row, and these having been 

 mistaken for spores gave origin to the name of Sjxrrendo- 

 nema, applied to this fungus. Mr. Cohn has described its 

 growth somewhat minutely and changed the generic name 

 to Mnpusa, or rather Euipm^h^a, 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 ofl" 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 w^ere found in the cavity of 

 Ihe abdomen of numerous flies in which the filaments were 

 traced in their earlier stages. Mr. Griflith inclines to regard 

 them as peridioles or spore-cases; or they may be stylo- 

 spores, w^hich 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 out^ward signs of the disease in its early stage; 

 yet w^atching 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- 

 less, constantly running and flying about; if the disease, 

 however, grows w^orse, their motions become ver\' sluggish, 

 and if you approach them with your fingers they either Ido 

 not fly away at all or in a very clumsy way, soon settling 

 .again. At last they are unable to w^alk more than a few 



