ALIMENTARY CANAL IN THE BEE 515 



in it, or, lastly, of its excretory role. We have hitherto only 

 established one fact for certain — the complete absence of fer- 

 ments in extracts from the small intestine of the bee. 



Large Intestine. 



The large intestine, similarly to the crop of the bee, presents 

 a thin-walled sac which is capable of expanding to enormous 

 dimensions, as seen by comparison of figs. 1 and 3 of PL 15. 

 During the whole winter the bees do not evacuate their excre- 

 ments, but continue taking food, on account of which their 

 large intestine becomes overfilled with faeces and swells into 

 a voluminous bladder. 



The scheme of structure of the large intestine is the same 

 as in the crop. In the anterior third of its wall are situated 

 six elongated cylindrical rectal glands (PI. 17, fig. 19, nj), the 

 microscopical structure of which was in general features 

 correctly described by Snodgrass and Petersen, 



We have also succeeded in establishing certain interesting 

 details elucidating the structure of these glands. From the part 

 of the cavity of the rectum each gland is covered by a chitinous 

 cuticle forming on the periphery of the organ a marginal fillet. 

 Within the gland there is an axial cavity (PI. 17, tig. 21, h) 

 dividing it into two parts — an exterior thin wall (iva) and 

 interior thick one (sn). The latter is formed by tall wedge- 

 shaped cells polyhedral in transverse section. 



The exterior wall is formed by two layers of minute poly- 

 gonal cells (PI. 17, fig. 21, wa). At the point where both walls 

 join together there lies a syncytial layer of cells containing 

 pigment inclusions (PL 17, fig. 21, sn). 



The exterior wall of the rectal gland (PL 17, tig. 20; 

 tig. 22, ica) is perforated in some places by tracheae (tr) which 

 pass into the cavity of the organ and penetrate with their 

 branches into its inner wall. 



To these data, which are to be found in the literature, we 

 may add the following : 



The ramitications of the tracheae passing to the thick 

 inner wall of the rectal gland pass along the edge of the poly- 



