PLATE XXI 



Figure 1. The alimentary canal of Tabaiius. ph., pharynx, 

 oes., oesophagus, pv., proventriculus. d.c., duct of 

 the crop, cr., crop, m.g., mid-gut, il., ileum. co., 

 colon, mp.t., Malpighian tubes, rt., rectum. X 25. 



Figure 2. Transverse section through the mid-gut of Tabanus, 

 showing the villi. tin., circular muscle fibres, l.m., 

 longitudinal fibres, tr., trachea, x 60. 



Figure 3. Cells of the proventriculus of same, between two of the 

 elevations in its wall, to show the external layer 

 of eosinophil material, x 500. 



Figure 4. A section through one of the mamillae of the proven- 

 triculus of same, showing the continuation into them 

 of the lumen, surrounded by the eosinophile layer. 

 The line of separation between the cells is very indis- 

 tinct in this region, mu., one of the irregular muscle 

 fibres in the wall, x 500. 



Figure 5. A villus from the mid-gut of Tabanus. X 250. 



Figure 6. A transverse section through the proventriculus of 

 same, about the level marked x in figure 1. X 150. 



