92 



Aug. 24 — Sept. 16 Human excrement ... ... ... 196 



The above observations are of gi-eat interest and importance 

 as indicating the breeding habits of the flies when they have 

 a choice of substances and under natural conditions, and are 

 confirmatory of my o^^^l experiments under laboratory conditions 

 where flies were confined in cages with the various substances 

 with a view to ascertaining not only whether they would deposit 

 their eggs on the substances in question, but also whether the 

 larvae could feed on them and the effect of the difierent sub- 

 stances upon the rate of development, of which mention is made 

 later. I also confirmed most of the laboratory results by breeding 

 flies from material exposed or collected in the open. As my ex- 

 periments were mainly carried (jut in England, many having been 

 since confirmed in Canada, the observations of Forbes, recorded 



