452 N. E. MCINDOO. 



but connect with the tops of the domes, he suggests that they 

 receive some kind of mechanical stimuli, although he performed 

 no experiments to determine their function. 



Lehr ('14), resuming the search for sense organs in Dytiscus 

 marginalis where left off by Hochreuther, found dome-shaped 

 organs on the elytra and wings. He found three main groups 

 in identically the same places as described by the present writer. 

 The number of pores in the group on the elytron varies from 130 

 to 150. The two main groups on the radius (his subcosta) of 

 the wing are large, but he did not count the pores in them. He 

 found a fourth group, consisting of about 30 pores, on the ventral 

 side of the costa near the base of the wing. He also found a few 

 scattered pores on the dorsal side of the costa just distal to the 

 fold of the wing, a few on the second cubitus, and a few irregularly 

 scattered along the full length of the media. Lehr has described 

 the anatomy of these organs almost identically as seen by the 

 present writer, but it seems that he has not correctly interpreted 

 some of the structures. He seems to think that each sense cell 

 is surrounded by another cell, but the latter cell is perhaps 

 nothing more than coagulated blood and the portion of it extend- 

 ing into the pore is certainly a hypodermal secretion forming the 

 cone as described in the preceding pages. His neurilemma 

 nuclei are perhaps hypodermal nuclei. He is able to trace the 

 sense fiber through the cone, but he has not recognized the small 

 opening through the dome. This is not surprising, because the 

 pores in the wings as so small that the openings or pore apertures 

 are never noticed unless first seen in the largest pores in the legs 

 or mouth parts. In the thinnest sections, the chitin forming the 

 dome is so thick as compared to the diameter of the pore aperture 

 that the aperture appears only as a streak slightly lighter than 

 the other chitin in the dome. Lehr has nothing to say about the 

 physiology of these organs. 



In experimenting with mutilated beetles, Hauser ('80) seems 

 to be the only one who has taken their longevity into considera- 

 tion. And even he has not kept an accurate record of their 

 behavior and longevity. He claims to have studied the behavior 

 of beetles before and after the removal of the antennse. When 

 the antennse were removed he ascertained that many beetles 



