ATJDITOEY SENSE OF HONEY-BEE 183 



chitin (represented by broken lines). Consequently, instead of 

 this articulation being weak, it is as strong as any other, and when 

 broken by a steady pull, the articular membrane remains fastened 

 to the third segment, showing that the knobs, although having 

 considerable play in their sockets, nevertheless lend considerable 

 strength to the articulation. 



Longitudinal sections through the second antennal segment 

 show the following: A large group of sense cells (fig. 12, SC) 

 hes on either side of the section; two large antennal nerves (N), 

 called internal and external olfactory nerves by Janet ('11)*, run 

 through the center of the segment and at various places unite 

 with the groups of sense cells, as shown in figure 12, and a large 

 trachea {Tr) runs near the nerves and sends out branches here 

 and there, 



A thorough study of these sections under an oil-immersion 

 lens shows the following: The elliptical sense cells (fig. 7, SC) 

 have conspicuous nuclei (Nuc), short nerve fibers (fig. 12, 'NF) 

 which run into the nerves, and long and comparatively large 

 sense fibers {SF) which run in bunches toward the articular mem- 

 brane. About half-wiay between the sense ceU and articular 

 membrane may be seen small slender nuclei (fig. 7, Nuc), some of 

 which seem to lie on the surface of the sense fibers, but it is more 

 likely that these are hypodermal nuclei, although the nuclei in 

 the hypodermis (fig. 12, Hyp) usually are round and much larger. 

 When the bunches of sense fibers reach the flexible strands of 

 chitin (C/i) the individual fibers separate, run between these 

 strands, then unite singly with the inner ends of the knobs {K), 



Figure 12 is a diagram showing most of the second segment in 

 longitudinal section and in perspective, and a small portion of 

 the third segment in both cross and longitudinal section and in 

 perspective. It is noted that the thin articular membrane 

 {ArtM)j bearing the chitinous knobs (K), is unprotected and 

 fully exposed to the outside air. Two of the knobs are cut length- 

 wise, showing the cone-shaped cavity which opens to the exterior. 

 The other knobs are heavily shaded, showing that they are buried 

 in the articular membrane. 



