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STRUCTURE, DEVELOPMENT, AND BIONOMICS OF HOUSE-FLY. 373 



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 /m in length ; it generally 

 contains a single oil-globule (o.g.). In a remarkable 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. Giard (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 may be 

 produced, and so on. By this peculiar arrangement the 

 conidia may eventually travel some distance, and it is no 

 doubt a great factor in the wide distribution of the fungus, 

 once it occurs. On the fly itself short conidiophores may be 

 found producing secondary conidia. 



Reproduction 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. dornestica 

 occurring indoors; they also produced conidia which he 

 identified as E. muscae. These azygospores measured 

 30-50 fj. in diameter, and were produced laterally or termin- 

 ally from hyphaa 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. muscae 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 



