STRUCTURE, DEVELOPMENT, AND BIONOMICS OF HOUSE-FLY. 378 
consequently deceased, fly. A conidium now develops 
(fig. 16) by the constriction of the apical region of the 
conidiophore. When it is ripe the conidium (fig. 17) is 
usually bell-shaped, measuring 25-30 n in length ; it generally 
contains a single oil-globule (o.y.). In a remai’kable manner it 
is now shot off from the conidiophore, often for a distance of 
about a centimetre, and in this way the ring or halo of white 
spores, which are seen around the dead fly, are formed. In 
some cases, although I find that it is not an invariable rule as 
some would suggest, the fly, when dead, is attached by its 
extended proboscis to the substratum. Griard (1879) found 
that blow-flies killed by Entomophthora calliphora were 
attached by the posterior end of the body. If the conidia, 
having been .shot off, do not encounter another fly, they have 
the power of producing a small conidiophore, upon which 
another conidium is in turn developed and discharged. If 
this is unsuccessful in reaching a fly a third conidium maybe 
produced, and so on. By this peculiar arrangement the 
conidia may eventually travel some distance, and it is no 
doubt a gi-eat factor in the wide distribution of the fungus, 
once it occurs. On the fly itself short conidiophores may be 
found producing secondary conidia. 
Keproduction by conidia appears to be the only form of 
generation, as we are still uncertain as to the occurrence of a 
resting-spore stage in this species. Winter (1881) states 
that he found resting-.spores in specimens of M. domestica 
occurring indoors; they also produced conidia which he 
identified as E. muse®. These azygospores measured 
30-50 n in diameter, and were produced laterally or termin- 
ally from hyph® within the infected fly. Giard (1. c.) describes 
resting spores which were produced externally and on 
specimens found in cool situations. Brefeld, however, is of 
the opinion that E. muse® does not produce resting-spores. 
The question of the production of resting-spores needs further 
investigation, as it is one of some importance. In the absence 
of confirmatory evidence it is extremely difficult to understand 
how the gap in the history of the Empusa, between the 
