616 E. N. PAVLOVSKY AND E. J. ZARIN 



hedral 'opitliolial cells (PL 17, figs. 23, 25, tr). The kyers of 

 protoplasm of tlu! latter adjacent to the tracheae consist of 

 a substance staining decsp black with lleideidiain's iron haema- 

 toxylin (PL 17, figs. 22, 25, z). 



These bordering layers differ from the alveolar-granular 

 j)t'()toplasm of the cells in their dentate aspect ; in some 

 individuals they resemble coarse intercellular bridges ; in 

 others they are more weakly expressed ; their striation, 

 however, is always visible in a greater or less degree. 



It is possible to trace the course of the tracheae to four-tifths 

 of the height of the cells. At this level the tracheae which have 

 hitherto pursued a radial course give ofi lateral branches 

 forming beneath the inner surface of the gland a network rich 

 in anastomoses (PL 17, fig. 24, tr). We did not observe anything 

 like the opening of ttie tracheae directly into the cavity of the 

 intestine in the rectum of the bee, as was described by Valle 

 in Diptera, 



The protoplasm of the large cells is in general granular 

 in some individuals with a fairly distinctly expressed alveolar 

 structure. The protoplasm is oxypliil. To the chitinous 

 cuticle is adjacent a layer of protoplasm staining less and 

 bearing the aspect of vesicles lying close to each other. The 

 nuclei of the cells described are of an irregular round shape. 

 They are disposed either in the middle part, or basally, depend- 

 ing upon the degree to which the protoplasm is tilled up with 

 granular inclusions. The nuclei are poor in chromatin. 



The variation in the contents of the cells described probably 

 is in connexion with the seasons of the year. In the hibernating 

 bee the large intestine of which had for several months been 

 filled up with faeces, the protoplasm of the large cells of 

 the rectal glands contains numerous globular inclusions and 

 minute granules (PL 17, fig. 21, gr). Both are oxyphil, wath 

 the exception of some of the larger granules. In some of 

 them are visible roundish portions not stained black with iron 

 haematoxylin. All these formations occupy the middle two- 

 thirds of the transverse section of the cell ; whilst in the basal 

 quarter of it lies the displaced nucleus (PL 17, fig. 21). 



