H. T. GiJssow 153 



control dishes dead flies, not infected with Empum, but at any rate 

 collected at a similar date (the previous autumn), which precaution 

 one would naturally expect in controlling the results of the first experi- 

 ment. It appears that he placed no "flies whatsoever on his control 

 dishes, which naturally remained sterile. Had he done so, we are 

 prepared to predict the identical formation of sporangia observed in 

 his experiments with Empusa killed flies. 



Next he made transfers from his culture, sporangia forming in the 

 secondary culture. '"Meanwhile," he states, "the fungus of his 

 secondary culture, which in every respect was identical with Mucor 

 racemosus, was transferred to a syrup made of sterilised sugar and 

 water, and put aside for experiments." How long he does not say. 

 Nor whether the spores had time to germinate in the sugar solution in 

 the "meantime." 



Now comes the most surprising effect! In his experiments Mr 

 Hesse uses "flies all bred from insects in confinement"; in June "the 

 chrvsahdes of the greater and lesser flies commenced hatching out" 

 ( ? Musca doniestica L. the common house fly, and Fannia canicularis, L. 

 the lesser house fly). In his ^rst experiment all negative results were 

 secured, owing apparently to absence of plum jam. Notwithstanding 

 an earlier statement by the authf»r that many insects became entangled 

 in the sticky mess of plum jam, in the second experiment this was used 

 together with, though not specifically so stated, a filter paper saturated, 

 as in the first experiment, with a syrup in which had been incorporated 

 spores (we take it Mucor spores). By the fourteenth day the first 

 deaths were noticed ; by the twenty-first day all flies were dead. " All 

 presented typical outward {sic) appearances of infection with Empusa 

 Muscae." No control was made in this case, he states. 



In experiment three, — a repetition of No. 2, — the first deaths 

 occurred in four days, and by the eleventh day all were dead. Cause 

 of death is not stated. 



In the fourth experiment there was a control with flies not fed 

 with "spores," and some fed with spores from the fourth generation 

 of Mucor. "The results were the same" (as which?). In the control 

 "no deaths occurred and the flies appeared to be normal four weeks 

 later." This is most remarkable; and, if Mr Hesse had not reported 

 this as an actual observation, I should feel inchned to challenge the 

 accuracy of these observations. 



Cultures were then made by this indefatigable worker from "flies 

 which had died in the cages wath the naked eye appearance of infection 



