412 THE GYPSY MOTH. 



also a small escape tube for the air to pass out. Sulphuric 

 acid was added to the potassic cyanide in flask A, and the 

 hydrocyanic acid gas passed through the sulphuric acid in 

 B, which thoroughly dried it ; it then passed out into C. 

 After the air had all passed out of C, the escape tube was 

 stopped. The gas was generated for an hour, after which 

 time an examination of the eggs showed no change, and 

 nearly all of them subsequently hatched. A duplicate ex- 

 periment gave similar results. January 13. Five egg- 

 clusters were treated with pure, concentrated hydrocyanic 

 acid gas for one hour and a half. None of the eggs hatched. 

 January 13. Five egg-clusters were treated for two hours 

 with hydrocyanic acid gas under a hood. An examination 

 of the eggs, made January 14, showed them to be slightly 

 dried, but, by March 24, about eight-tenths of the eggs had 

 hatched. January 15. Five egg-clusters were treated with 

 hydrocyanic acid gas for fifteen minutes. The eggs did not 

 appear to be affected, although none of them hatched. 



Hydrogen Arsenide. April 7. Five egg-clusters were 

 treated for fifteen minutes with hydrogen arsenide, made by 

 pouring a solution of arsenic into a mixture of granulated 

 zinc and hydrochloric acid. None of these eggs hatched. 

 November 5. A number of egg-clusters were treated for 

 one hour with hydrogen arsenide. None of the eggs 

 hatched. February 6. About twenty-five broken egg-clus- 

 ters were treated with hydrogen arsenide for forty-five 

 minutes. The gas was made as follows : A solution of 

 arsenic was poured into a mixture of hydrochloric acid and 

 zinc. The gas which was given off was dried by passing 

 through a U tube containing calcium chloride, then into the 

 bottle containing the eggs. None hatched. Several other 

 experiments with this gas gave similar results. 



Hydrogen Sulphide. April 7. Some egg-clusters were 

 submitted to the action of hydrogen sulphide for ten 

 minutes. At the end of this time the eggs were shrivelled 

 and none hatched. January 30. Several egg-clusters were 

 treated for one hour with hydrogen sulphide gas, which was 

 made by adding dilute sulphuric acid to iron sulphide. It 

 was passed through a U tube and then into a bottle con- 



