164 THE FUNGAL DISEASE: EM P USA MUSCAE COHN 



off from the conidiophore, usually for a distance of about a centi- 

 metre, although I have seen spores discharged to a distance of 

 70 mm. In this way the ring or halo of white spores, which are 

 seen around the dead fly, are formed. My friend Mr H. T. Giissow 

 has confirmed in conjunction with me the external infection by 

 the conidiospores. He has also found that the conidiospores may 

 be taken up through the mouth, and fig. 74 shows the pro- 

 boscis marks of flies which have been feeding on the discharged 

 conidiospores. 



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 gene- 

 ration, 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. muscae. 

 These azygospores measured 30-50 fx in diameter, and were pro- 

 duced laterally or terminally from hyphae within the infected fly. 

 Giard (I.e.) 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 investi- 

 gation, and 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 late autumn of 

 one year and the summer of the next, is filled. A number of sug- 

 gestions have been made, many of which cannot be accepted ; for 



