544 PROCEEDINGS OF THE ACADEMY OF [Aug., 



Fig. 2 is a diagram of the articular membrane, removed from the 

 abdomen and spread out flat under a low-power lens. This membrane 

 . in the living bee is shiny and appears to be covered with a trans- 

 parent liquid. The anterior margin of the membrane is bordered 

 by small barbed hairs (fig. 2, a) on the fifth tergum, and the posterior 

 margin is bordered by smaller spinelike hairs (fig. 2, h) on the sixth 

 tergum. The chitin of the posterior portion (fig. 2, PostP) of this 

 membrance is thinner than is the chitin of the tergum, but it is 

 strengthened near its centre by a narrow and heavy vein (figs. 1 and 

 2, e), and at its anterior margin there is a heavier and much wider 

 vein (figs. 1 and 2, d). 



The chitin of the anterior portion (fig. 2, AntP) of the membrane 

 is much thinner than is that of the posterior portion. It is quite 

 flexible and for this reason may be easily folded to form the canal. 

 Instead of it being perfectly smooth, as is the posterior portion of 

 the membrane, its surface is covered with innumerable minute, 

 narrow, groovelike indentations. These may be comparatively 

 long or short, bent, tortuous, or straight and seemingly extend half 

 way through the chitin. The small lines in fig. 2, c, represent their 

 arrangement and fig. 3 represents a few of them seen under a high 

 magnification. Of course, they are not slits passing entirely through 

 the chitin, but they are grooves and pass about one half through 

 the membrane. 



Looking through the chitin of the posterior portion (fig. 2, PostP) 

 of the articular membrane, at a deeper focus, may be seen many 

 round cells, each of which has a tube that runs to the surface of the 

 membrane. In fig. 2, 115 of these tubes with cells are shown, but 

 in all there are from 500 to 600. The majority of the tubes have 

 exits in the chitin between the two heavy veins (figs. 1, Plate XIX, 

 and 2, d and c), but none of them has an exit in the chitin of the 

 anterior portion (AntP) of the membrane. The place where these 

 tubes empty is best seen in fig. 1, Tu. It is thus seen that the tubes 

 unite with the posterior wall of the canal which is formed by the 

 heavy chitin between d and e in figs. 1 and 2. The bottom and 

 anterior wall of the canal are formed by the anterior portion of the 

 articular membrane. 



Fig. 4 represents four of the cells and several of the tubes seen 

 under a high-power lens, a represents comparatively thin and almost 

 transparent chitin; b is a narrow, thick, and yellow band of chitin; 

 c is a thick, semitransparent band of chitin; d is a wide, thick, and 

 opaque band of chitin; e is thick, semitransparent chitin. It is 



