DEVELOPMENT OF EMl'USA MUSCAE 



163 



explained their presence as being due to spontaneous generation ; 

 he believed that the tly first became diseased and that the fungus 

 followed in consequence. After a period of two or three days the 

 fly's body will be found to be completely penetrated by the fungus, 

 which destroys all the internal tissues and organs. The wiiole 

 body is filled with the gemmae, which germinate and produce 

 ramifying hyphae (fig. 73, a). 



The latter pierce the softer portions of the body-wall between 

 the segments and produce the short, stout conidiophores (c), which 



Fig. 74. Discharged conidia of Empusa viuscae upon which M. domestica has been 

 feeding as indicated by the proboscis marks. (Photo by H. T. Giissow.) 



are closely packed together in a palisade-like mass to form a 

 compact white cushion of conidiophores, which is the transverse 

 white ring that one finds between each of the segments of a 

 diseased, and consequently deceased, fly. A conidium now develops 

 (fig. 73, b) by the constriction of the apical region of the conidio- 

 phore. When it is ripe the conidium (fig. 73, c) is usually bell- 

 shaped, measuring 25-30 /x in length ; it generally contains a 

 single oil-globule (o.g.). In a remarkable manner it is now shot 



11—2 



