EXPERIMENT STATION BULLETINS. 



541 



the least trace of oxygen, turns brown, then dark. In the experiments, 

 results of which are given here, "H" remained clear or light straw- 

 color. The solutions in "F" and '*E" were stained but slightly. As- 

 sured, in this way of pure hydrogen, the beetles were prepared for the 

 experiment. Four specimens of Passaliis cornutus were selected, 

 brushed clean, and weighed. From one of these beetles the elytra and 

 wings could be removed with almost no injury whatever. Stop "S" 

 was now closed. The wingless beetle was quickly placed, dorsal sur- 

 face up, in the cell "J" — the other three beetles in ''K." Connections 

 were closed at once and "S" opened. Hydrogen flowed rapidly, due 



Fig. 1. Apparatus used to keep insects under obser\ ation in a continous flow of pure hydrogen. 



to the storage and pressure gained while ''S" was closed, so that any 

 oxygen introduced with the beetles into "J" and "K" must rapidly have 

 been washed through. Noav, with cell ''J" upon the stand of a binocu- 

 lar microscope, the heart, and some other internal organs of the naked 

 beetle inclosed could easily be seen through the thin transparent chitin 

 of the dorsal abdominal surface. Also the movements of beetles in 

 ^'K" could be readily noted. After one-half hour, the small amount of 

 oxygen introduced into "J" and "K" had been entirely replaced by 

 hydrogen and. then the standard barium hydrate was carefully intro 

 duced into "L" and ''M." The beetles were under constant observa- 

 tion for the first ten to twelve hours and at intervals after that. A 

 slow stream of hydrogen was kept bubbling continuously to the end 

 of the experiment. 



Some results of these experiments may, perhaps, be best given in 

 tabular form. 



All text Figs, in this bulletin were drawn, under supervision, by Mr. A. D. Baurod. 



