184 N. E. McINDOO 
A glance at figure 12 shows that the articular membrane re- 
sembles the head of a drum and that the knobs act chiefly as 
sense-fiber attachments. It is evident, judging merely from 
the structure of this organ, that gusts of wind and possibly weak 
air currents would cause the articular membrane to vibrate, there- 
by irritating the sense cells. This organ might also receive jar 
Fig. 12 Diagram, representing most of second antennal segment of worker 
honey-bee in longitudinal section and in perspective and a small portion of third 
segment in both cross and longitudinal section and in perspective, showing John- 
ston’s organ which consists of two large groups of sense cells (SC) whose nerve 
fibers (VF) run into the two antennal nerves (NV) and whose sense fibers (SF) 
are attached to the knobs (K) in the articular membrane (ArtM). Two of the 
knobs are cut lengthwise, showing the cone-shaped cavity which opens to the 
exterior, while the other knobs are heavily shaded, indicating that they are 
buried in the articular membrane. JT'r, trachea; Hyp, hypodermis; Ch, hard 
chitin; and Chi, soft, flexible strands of chitin which firmly bind second and 
third segments together. 
