308 THE AMERICAN NATURALIST [Vol. XLV 



form larger trachea? ; the latter lie nearly flat against the 

 inside surface of this reflecting layer, and run diag- 

 onally outward, finally uniting almost at the spiracle 

 with the breathing trachea*, with which they are iden- 



side of tlie/abdomen, one near either edge of each seg- 

 ment, and are furnished with some valvular arrangement 

 at their orifice ; the details of this structure have not yet 

 been clearly made out. The arrangement of the smaller 

 tracheae and tracheoles is much the same in all three 

 species. The trachea? pass through the reflecting layer 

 and the photogenic tissue perpendicularly to the surface. 

 These trachea' are furnished with chitinous hairs on the 



