128 Psyche [August 



jar was then introduced a small glass beaker containing a bit of 

 carefully inspected fish meat. The jar was then closed by having 

 mosquito netting tied over its open end and by setting in place 

 on this netting the glass cover of the jar without, however, 

 clamping it down. Thus it was believed that the jars were 

 effectively protected against the introduction of eggs from the 

 outside and that the gases generated by the decomposing meat 

 within could escape. Fluid could be introduced into the jar by 

 removing the glass top and pouring it in through the meshes 

 of the netting without, however, allowing the accidental en- 

 trance or escape of flies should there be any at hand. The fish- 

 meat in the jars was not sterilized by cooking, for it was found 

 to decompose much more freely and satisfactorily when un- 

 cooked. 



The fifty jars thus prepared were set aside April 2, 1919, 

 and allowed to stand twenty days. After this period a searching 

 inspection showed that none of them contained maggots. These 

 would surely have been seen had they been introduced by ac- 

 cident with the meat. On April 23 twenty-five jars were infected 

 each with a single fly egg and the remaining twenty-five were 

 held unchanged as checks. From time to time during the next 

 few weeks a small amount of distilled water was poured into 

 each jar but otherwise the jars remained closed for this period. 

 On May 14 the contents of the jars were examined. The twenty- 

 five jars used as checks contained no evidence of flies. In the 

 twenty-five infected jars seven were without maggots or pupae 

 and eighteen contained each a single pupa. Thus there was no 

 evidence of increase. A second trial carried out in the same way 

 in May and June yielded similar results. 



In the autumn of 1919 tests were resumed. These were of 

 two kinds,, one to ascertain what hatched from an individual 

 egg and the other to find out what came from the larva. To de- 

 termine what came from a single egg, twenty eggs on October 29 

 were put with a few drops of water each into a separate Syracuse 

 watch-glass. Twelve of these had hatched by October 80 and 

 each produced a single larva. Eight failed to hatch probably 

 because of mechanical injurj^ Between October and the end of 



